Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the alpha subunit of the Torpedo nicotinic cholinergic receptor (AChR), a sequence region surrounding a pair of adjacent cysteinyl residues at positions 192 and 193 contributes to a binding site for cholinergic ligands, including the snake alpha-neurotoxins. Synthetic and biosynthetic peptides corresponding to this region bind alpha-bungarotoxin (alpha-BTX) in the absence of other structural components of the AChR and, therefore, represent a "prototope" for alpha-BTX. Using synthetic peptides corresponding to the complete AChR alpha subunits of Torpedo electroplax and mammalian muscle, we previously defined a sequence segment corresponding to a universal prototope for alpha-BTX binding between amino acid residues 181 and 200 [Conti-Tronconi, B. M., Tang, F., Diethelm, B. M., Spencer, S. R. Reinhardt-Maelicke, S., & Maelicke, A. (1990) Biochemistry 29, 6221-6230; McLane, K. E., Wu, X., & Conti-Tronconi, B. M. (1990) J. Biol. Chem. 265, 1537-1544]. To elucidate the structural requirements for alpha-BTX binding, we initially used nonconservative single amino acid substitution analogues of the parental alpha(181-200) sequence, and we found that residues at positions 188-190 (VYY), and 192-194 (CCP) and several flanking residues seemed to be involved in alpha-BTX binding [Conti-Tronconi, B. M., Diethelm, B. M., Wu, X., Tang, F., Bertazzon, A., & Maelicke, A. (1991) Biochemistry 30, 2575-2584]. In the present study, amino acid residues previously found to affect alpha-BTX binding were replaced by different conservative single amino acid substitutions, in order to determine the nature of the amino acid side-chain interactions with alpha-BTX. Whereas V188 could be replaced by Ile or Thr with minor effects on alpha-BTX binding, substitution of Phe, His, or Thr for Y189 and Y190 resulted in large to moderate decreases in alpha-BTX binding. Similarly, alpha-BTX binding activity was intolerant to substitutions of C192 or C193 with Ser, His, or Val. Structural changes of the peptide alpha(181-200) induced by substitution of P194 or P197 with two adjacent Gly residues, and insertion of a Gly between C192 and C193, were also incompatible with alpha-BTX binding. Conservative substitutions of other aliphatic and aromatic residues resulted in only minor effects on alpha-BTX binding, as did replacements of K185 and D195 that changed or maintained the charge distribution of peptide alpha (181-200). The recognition site for alpha-BTX formed by the prototope alpha(181-200), therefore, involves important interactions with Y189, Y190, C192, and C193 that are highly specific to the amino acid residue at that position.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:An alpha-bungarotoxin-binding sequence on the Torpedo nicotinic acetylcholine receptor alpha-subunit: conservative amino acid substitutions reveal side-chain specific interactions. 811 19

Dipeptidyl peptidase II (DPP II) was purified to homogeneity from porcine seminal plasma by polyacrylamide gel electrophoresis (PAGE). The molecular weight of the purified enzyme was calculated to be approx. 185,000 and 200,000 on Superdex 200 column chromatography and non-denatured PAGE, respectively, and to be 58,000 and 61,000 on SDS-PAGE in the absence and presence of beta-mercaptoethanol (beta-ME), respectively. These findings suggested that the enzyme is composed of three identical subunits. The enzyme rapidly hydrolyzed the substrates Lys-Ala-MCA and Gly-Pro-MCA at acidic pH. The Km and V(max) values of DPP II at optimal pH (pH 6.0) were 1330 microM and 2.9 mumol/mg per min for Gly-Pro-MCA, and 360 microM and 1.43 mumol/mg per min for Lys-Ala-MCA, respectively. It was strongly inhibited by diisopropylphosphofluoride (DFP), and moderately by 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). These findings suggest that DPP II is a serine peptidase. Furthermore, the enzyme activity was also strongly inhibited by copper ions. The amino-acid sequence of the first 41 residues of the enzyme was determined as Ala1-Ser-Pro-Pro-Glu-Pro-Gly-Phe-Arg- Glu10-Val-Tyr-Phe-Glu-Gln-Leu-Leu-Asp-His-Phe20-Asn-Phe-Glu- Arg-Phe- Gly-Lys-Lys-Thr-Phe30-Arg-Gln-Arg-Phe-Leu-Val-Ser-Asp-Lys-Phe40 -Trp. This sequence showed homology (11.6-30.2%) to the N-terminal amino-acid sequences of cytotoxic cell proteinases (CCP 1-4), granzymes. Other properties of DPP II including pH optimum, pH stability, and heat stability were characterized.
 ...
PMID:Dipeptidyl peptidase II from porcine seminal plasma: purification, characterization, and its homology to granzymes, cytotoxic cell proteinases (CCP 1-4). 864 18

The requirement of cytochrome c-550 (PSII-V) in photosystem II (PSII) has been assessed in Synechocystis sp. PCC 6803 containing mutations between Gly-351 and Thr-436 of the loop E domain of the chlorophyll a-binding protein CP47. Six photoautotrophic strains were utilized to compare the effect of removal of either the manganese-stabilizing protein (PSII-O) or PSII-V on PSII activity in vivo. These were a wild-type control; two strains with amino acid deletions, Delta(R384-V392) and Delta(G429-T436); and three carrying specific amino acid substitutions, G351L/T365Q, G351L/E364Q/T365Q, and G351L/E353Q/E355Q/T365Q. The removal of PSII-O prevented the assembly of PSII in Delta(G429-T436) but not in Delta(R384-V392). Neither Delta(G429-T436) nor Delta(R384-V392) could support photoautotrophic growth in the absence of PSII-V. In chloride-limiting conditions, the photoautotrophic growth of Delta(R384-V392) was severely impaired and that of Delta(G429-T436) totally inhibited, and no strains lacking PSII-V could grow in chloride-limiting or calcium-limiting media. Substitutions at Gly-351, Glu-353, Glu-355, and Thr-365 produced phenotypes that were similar to those of the control in the presence or absence of PSII-O and PSII-V, but removal of PSII-O from G351L/E364Q/T365Q produced a significant reduction of assembled PSII centers and an enhanced sensitivity to photoinactivation while removal of PSII-V prevented photoautotrophic growth. The additional mutants E364Q:DeltaPSII-V and E364G:DeltaPSII-V demonstrated that this inhibition was a consequence of the mutation at Glu-364. These results also show that the removal of PSII-V, in vivo, produces phenotypes in the CP47 mutants examined that are either similar or more severe than those resulting from the removal of PSII-O.
 ...
PMID:Specific requirements for cytochrome c-550 and the manganese-stabilizing protein in photoautotrophic strains of Synechocystis sp. PCC 6803 with mutations in the domain Gly-351 to Thr-436 of the chlorophyll-binding protein CP47. 977 70

The deletion of the amino acids between Gly-351 and Thr-365 within the large, lumen-exposed, hydrophilic region (loop E) of the photosystem II (PSII) chlorophyll a-binding protein CP47 produced a strain of Synechocystis sp. PCC 6803 that failed to assemble stable PSII centers [Eaton-Rye, J. J., and Vermaas, W. F. J. (1991) Plant Mol. Biol. 17, 1165-1177]. The importance of two conserved Phe residues at positions 362 and 363 within this deletion has been investigated. The F363R strain had impaired photoautotrophic growth and an enhanced sensitivity to photoinactivation, demonstrating that Phe is required at position 363 for normal PSII function. In contrast, photoautotrophic growth in strains N361K and F362R was unaffected. Uniquely, among the mutant strains tested, F363R was unable to grow under chloride-limiting conditions, and this effect was reversed by replacing chloride with bromide. The removal of the manganese-stabilizing protein (PSII-O), the 12 kDa extrinsic protein (PSII-U), and cytochrome c-550 (PSII-V) was investigated in each mutant in vivo. In N361K and F362R, removal of PSII-V produced a more deleterious effect than the removal of PSII-O, but even so, all strains remained photoautotrophic. In contrast, the absence of PSII-V and PSII-O in F363R produced obligate photoheterotrophic strains. The removal of PSII-U increased the susceptibility of PSII to heat inactivation and further decreased the stability of PSII in F363R, demonstrating that PSII-U can contribute to the stabilization of mutations that have been introduced into CP47. The order of importance of the selective removal of the extrinsic proteins in strains carrying mutations in loop E of CP47 was found to be as follows: DeltaPSII-V >/= DeltaPSII-O > DeltaPSII-U.
 ...
PMID:Mutation of Phe-363 in the photosystem II protein CP47 impairs photoautotrophic growth, alters the chloride requirement, and prevents photosynthesis in the absence of either PSII-O or PSII-V in Synechocystis sp. PCC 6803. 1005 41

Tetrahydrobiopterin (BH4)-glucoside was identified from Synechococcus sp. PCC 7942 by HPLC analysis and the enzymatic activity of a glycosyltransferase producing the compound from UDP-glucose and BH4. The novel enzyme, named UDP-glucose:BH4 glucosyltransferase, has been purified 846-fold from the cytosolic fraction of Synechococcus sp. PCC 7942 to apparent homogeneity on SDS-PAGE. The native enzyme exists as a monomer having a molecular mass of 39.2 kDa on SDS-PAGE. The enzyme was active over a broad range of pH from 6.5 to 10.5 but most active at pH 10.0. The enzyme required Mn(2+) for maximal activity. Optimum temperature was 42 degrees C. Apparent K(m) values for BH4 and UDP-glucose were determined as 4.3 microM and 188 microM, respectively, and V(max) values were 16.1 and 15.1 pmol min(-1) mg(-1), respectively. The N-terminal amino acid sequence was Thr-Ala-His-Arg-Phe-Lys-Phe-Val-Ser-Thr-Pro-Val-Gly-, sharing high homology with the predicted N-terminal sequence of an unidentified open reading frame slr1166 determined in the genome of Synechocystis sp. PCC 6803, which is known to produce a pteridine glycoside cyanopterin.
 ...
PMID:Purification and characterization of UDP-glucose:tetrahydrobiopterin glucosyltransferase from Synechococcus sp. PCC 7942. 1111 66

Recombinant plant-type asparaginases from the cyanobacteria Synechocystis sp. PCC (Pasteur culture collection) 6803 and Anabaena sp. PCC 7120, from Escherichia coli and from the plant Arabidopsis thaliana were expressed in E. coli with either an N-terminal or a C-terminal His tag, and purified. Although each of the four enzymes is encoded by a single gene, their mature forms consist of two protein subunits that are generated by autoproteolytic cleavage of the primary translation products at the Gly-Thr bond within the sequence GTI/VG. The enzymes not only deamidated asparagine but also hydrolysed a range of isoaspartyl dipeptides. As various isoaspartyl peptides are known to arise from proteolytic degradation of post-translationally altered proteins containing isoaspartyl residues, and from depolymerization of the cyanobacterial reserve polymer multi-L-arginyl-poly-L-aspartic acid (cyanophycin), plant-type asparaginases may not only function in asparagine catabolism but also in the final steps of protein and cyanophycin degradation. The properties of these enzymes are compared with those of the sequence-related glycosylasparaginases.
 ...
PMID:Isoaspartyl dipeptidase activity of plant-type asparaginases. 1198 85

In previous work, some members of our group isolated mutant strains of Synechocystis sp. strain PCC 6803 in which point mutations had been inserted into the psaC gene to alter the cysteine residues to the F(A) and F(B) iron-sulfur clusters in the PsaC subunit of photosystem I (J. P. Yu, I. R. Vassiliev, Y. S. Jung, J. H. Golbeck, and L. McIntosh, J. Biol. Chem. 272:8032-8039, 1997). These mutant strains did not grow photoautotrophically due to suppressed levels of chlorophyll a and photosystem I. In the results described here, we show that suppressor mutations produced strains that are capable of photoautotrophic growth at moderate light intensity (20 micromol m(-2) s(-1)). Two separate suppressor strains of C14S(PsaC), termed C14S(PsaC)-R62 and C14S(PsaC)-R18, were studied and found to have mutations in a previously uncharacterized open reading frame of the Synechocystis sp. strain PCC 6803 genome named sll0088. C14S(PsaC)-R62 was found to substitute Pro for Arg at residue 161 as the result of a G482-->C change in sll0088, and C14S(PsaC)-R18 was found to have a three-amino-acid insertion of Gly-Tyr-Phe following Cys231 as the result of a TGGTTATTT duplication at T690 in sll0088. These suppressor strains showed near-wild-type levels of chlorophyll a and photosystem I, yet the serine oxygen ligand to F(B) was retained as shown by the retention of the S > or = 3/2 spin state of the [4Fe-4S] cluster. The inactivation of sll0088 by insertion of a kanamycin resistance cartridge in the primary C14S(PsaC) mutant produced an engineered suppressor strain capable of photoautotrophic growth. There was no difference in psaC gene expression or in the amount of PsaC protein assembled in thylakoids between the wild type and an sll0088 deletion mutant. The sll0088 gene encodes a protein predicted to be a transcriptional regulator with sequence similarities to transcription factors in other prokaryotic and eukaryotic organisms, including Arabidopsis thaliana. The protein contains a typical helix-turn-helix DNA-binding motif and can be classified as a negative regulator by phylogenetic analysis. This suggests that the product of sll0088 has a role in regulating the biogenesis of photosystem I.
 ...
PMID:Suppressor mutations in the study of photosystem I biogenesis: sll0088 is a previously unidentified gene involved in reaction center accumulation in Synechocystis sp. strain PCC 6803. 1281 82

Changes in the chemical structure of alpha-carboxylate of the D1 C-terminal Ala-344 during S-state cycling of photosynthetic oxygen-evolving complex were selectively measured using light-induced Fourier transform infrared (FTIR) difference spectroscopy in combination with specific [(13)C]alanine labeling and site-directed mutagenesis in photosystem II core particles from Synechocystis sp. PCC 6803. Several bands for carboxylate symmetric stretching modes in an S(2)/S(1) FTIR difference spectrum were affected by selective (13)C labeling of the alpha-carboxylate of Ala with l-[1-(13)C]alanine, whereas most of the isotopic effects failed to be induced in a site-directed mutant in which Ala-344 was replaced with Gly. Labeling of the alpha-methyl of Ala with l-[3-(13)C]alanine had much smaller effects on the spectrum to induce isotopic bands due to a symmetric CH(3) deformation coupled with the alpha-carboxylate. The isotopic bands for the alpha-carboxylate of Ala-344 showed characteristic changes during S-state cycling. The bands appeared prominently upon the S(1)-to-S(2) transition and to a lesser extent upon the S(2)-to-S(3) transition but reappeared at slightly upshifted frequencies with the opposite sign upon the S(3)-to-S(0) transition. No obvious isotopic band appeared upon the S(0)-to-S(1) transition. These results indicate that the alpha-carboxylate of C-terminal Ala-344 is structurally associated with a manganese ion that becomes oxidized upon the S(1)-to-S(2) transition and reduced reversely upon the S(3)-to-S(0) transition but is not associated with manganese ion(s) oxidized during the S(0)-to-S(1) (and S(2)-to-S(3)) transition(s). Consistently, l-[1-(13)C]alanine labeling also induced spectral changes in the low frequency (670-350 cm(-1)) S(2)/S(1) FTIR difference spectrum.
 ...
PMID:Structural changes of D1 C-terminal alpha-carboxylate during S-state cycling in photosynthetic oxygen evolution. 1554 97

Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can fix N2 in differentiated cells called heterocysts. The products of Anabaena open reading frames (ORFs) all1046, all1047, all1284, alr1834 and all2912 were identified as putative elements of a neutral amino acid permease. Anabaena mutants of these ORFs were strongly affected (1-12% of the wild-type activity) in the transport of Pro, Phe, Leu and Gly and also impaired (17-30% of the wild-type activity) in the transport of Ala and Ser. These results identified those ORFs as the nat genes encoding the N-I neutral amino acid permease. According to amino acid sequence homologies, natA (all1046) and natE (all2912) encode ATPases, natC (all1047) and natD (all1284) encode transmembrane proteins, and natB (alr1834) encodes a periplasmic substrate-binding protein of an ABC-type uptake transporter. The natA, natC, natD and natE mutants showed defects in Gln and His uptake that were not observed in the natB mutant suggesting that NatB is not a binding protein for Gln or His. The nat mutants released hydrophobic amino acids to the medium, and amino acid release took place at higher levels in cultures incubated in the absence of combined N than in the presence of nitrate. Alanine was the amino acid released at highest levels, and its release was impaired in a mutant unable to develop heterocysts. The nat mutants were also impaired in diazotrophic growth, with natA, natC, natD and natE mutants showing more severe defects than the natB mutant. Expression of natA and natC, which constitute an operon, natCA, as well as of natB was studied and found to take place in vegetative cells but not in the heterocysts. These results indicate that the N-I permease is necessary for normal growth of Anabaena sp. strain PCC 7120 on N2, and that this permease has a role in the diazotrophic filament specifically in the vegetative cells.
 ...
PMID:ABC-type neutral amino acid permease N-I is required for optimal diazotrophic growth and is repressed in the heterocysts of Anabaena sp. strain PCC 7120. 1613 26

The Pho regulon is controlled by the histidine kinase-response regulator pair SphS-SphR in many cyanobacteria and up-regulation of the Pho regulon can be monitored by measuring alkaline phosphatase activity. However, the mechanism regulating signal transduction between SphS and SphR has not been described. We have created a cyanobacterial strain allowing the introduction of mutations into the transmitter domain of SphS. Mutations at Thr-167, adjacent to the H motif of SphS, introduce elevated alkaline phosphatase activity in the presence of phosphate and an enhancement of alkaline phosphatase activity, when compared to the control strain, in phosphate-limiting media. SphU acts as a negative regulator of the SphS-SphR system in Synechocystis sp. PCC 6803 and we show that constitutive alkaline phosphatase activity in the absence of SphU requires signal transduction through SphS and SphR. However, constitutive activity in the absence of SphU is severely attenuated in the DeltaSphU:SphS-T167N mutant. Our data suggest that Thr-167 contributes to the mechanism underlying regulation by SphU. We have also assembled a deletion mutant system allowing the introduction of mutations into SphR and show that Gly-225 and Trp-236, which are both conserved in SphR from cyanobacteria, are essential for activation of the Pho regulon under phosphate-limiting conditions.
 ...
PMID:Phosphate sensing in Synechocystis sp. PCC 6803: SphU and the SphS-SphR two-component regulatory system. 1754 76


<< Previous 1 2 3 Next >>