Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glycoprotein hormones are heterodimeric and contain a common alpha-subunit, which is noncovalently associated with a hormone-specific beta-subunit. The alpha-subunit has been highly conserved throughout evolution; for example, the five amino acid residues of the carboxy-terminus, Tyr-Tyr-His-Lys-Ser-COOH, are identical in nine of the 10 available amino acid sequences. It has been shown that enzymatic removal of these five amino acid residues, while not affecting holoprotein formation, results in a heterodimer that exhibits very little, if any, binding to the CG/LH receptor. Using site-directed mutagenesis on the human alpha-subunit, we have prepared two deletion mutants, Des-(88-92)alpha and Des-(89-92)alpha, and two point mutants, where each of the two tyrosines, 88 and 89, was replaced with phenylalanine, in order to delineate more specifically the contributions of these aromatic side-chains to receptor binding. The cDNAs for wild-type hCG alpha and mutants were introduced into a pcDNAINEO expression vector, and the cDNA for hCG beta was inserted into a pRSV plasmid; both were transiently cotransfected into DUXB-11 cells. The media were collected, and RIAs showed that all mutants formed heterodimers; moreover, there was no discernable difference in subunit assembly between wild-type hCG alpha and the various mutant alpha-subunits. The gonadotropin mutants were assayed in vitro using a competitive binding assay with [125I]hCG and stimulation of progesterone production in the transformed murine Leydig cell line MA-10.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1992 Jun
PMID:The carboxy-terminal region of the glycoprotein hormone alpha-subunit: contributions to receptor binding and signaling in human chorionic gonadotropin. 137 73

Photochemically induced dynamic nuclear polarization (photoCIDNP) measurements, specific for exposed tyrosine residues, have been applied to elucidate conformational differences responsible for the immunological diversity of the synthetic multichain copolymers, Tyr1Tyr2Glu3Glu4-poly-DL-Ala-poly-Lys and Tyr1Glu2Tyr3Glu4-poly-DL-Ala-poly-LS. These two copolymers are essentially identical in their molecular weight, size, shape and composition, and differ only in the order of the two internal amino acid residues within the sequence of the tetrapeptide epitopes. Nonetheless, previous studies have shown that the two macromolecules behave differently, as evidenced by their immunological and immunogenic properties. As immunogens they act under different genetic control mechanisms, and differ in their interactions with antigen presenting cells, T cells and B cells. Antibodies elicited against these two antigens do not cross react. The photoCIDNP measurements of these two polymers, intended to elucidate discrete structural differences controlling immune recognition, showed that in the TyrTyrGluGlu polymer, Tyr1 and Tyr2 rings are free, non-interacting and undergo fast internal rotation. Computed minimum energy conformations confirm these conclusions and indicate that Tyr1 and Tyr2 point to different regions in space. In TyrGluTyrGlu, however, CIDNP measurements give rise to one broad tyrosine 3,5 proton signal, the result of a strong Tyr1-Tyr3 hydrophobic interaction. These two tyrosine residues are thus close in space, and undergo slow internal rotation. These results are in agreement with the computed minimum energy conformations.
Mol Immunol 1992 Sep
PMID:Structural origin of the immunological diversity of two closely related tetrapeptides: CIDNP study of TyrTyrGluGlu and TyrGluTyrGlu epitopes. 137 76

Extensins comprise a family of structural cell wall hydroxyproline-rich glycoproteins in plants. Two tomato genomic clones, Tom J-10 and Tom L-4, were isolated from a tomato genomic DNA library by in situ plaque hybridization with extensin DNA probes. Tom J-10 encoded an extensin with 388 amino acid residues and a predicted molecular mass of 43 kDa. The Tom J-10 encoded extensin lacked a typical signal peptide sequence, but contained two distinct protein domains consisting of 19 tandem repeats of Ser-Pro4-Ser-Pro-Lys-Tyr-Val-Tyr-Lys at the amino terminus which were directly followed by 8 tandem repeats of the consensus sequence Ser-Pro4-Tyr3-Lys-Ser-Pro4-Ser-Pro at the carboxy terminus. RNA blot hybridization analysis with the Tom J-10 extensin probe demonstrated the presence of a 4.0 kb tomato stem mRNA which accumulated markedly in response to wounding. Tom L-4 encoded an extensin with 322 amino acid residues and a predicted molecular mass of 35 kDa. The Tom L-4 encoded extensin contained a typical signal peptide sequence at the amino terminus and was followed by at least 3 distinct domains. These domains consisted of an amino terminal domain containing several Lys-Pro and Ser-Pro4 repeat units, a central domain with repeats of the consensus sequence Ser-Pro2-5-Thr-Pro-Ser-Tyr-Glu-His-Pro-Lys-Thr-Pro, and a carboxy terminal domain containing repeats of the consensus sequence Ser-Ser-Pro4-Ser-Pro-Ser-Pro4-Thr-Tyr1-3. RNA blot hybridization analysis with the Tom L-4 extensin probe demonstrated the presence of a 2.6 kb tomato stem mRNA which accumulated in response to wounding.
Plant Mol Biol 1992 Oct
PMID:Isolation and characterization of two wound-regulated tomato extensin genes. 138 Dec 33

Myelin basic protein (MBP) and P0 glycoprotein are major structural proteins of myelin. In adult frog, MBP is found in both the central and peripheral nervous systems (CNS and PNS), while P0 is found exclusively in the PNS. To assess the phylogenetic conservation of these proteins, MBP and P0 were isolated from adult bull-frog. A cyanogen bromide cleavage peptide of MBP (8-26), and the amino-terminal region (1-20) and an endoproteinase Lys-C peptide (67-79) of P0 were sequenced and compared to those of other vertebrate species. Residues that were conserved among other vertebrate species were found also to be conserved in frog: MBP--Ala18, Ser19, Thr20, Asp22; P0--Ile1, Val3, Thr5, Val13, Gly14, Ser15, Val17, Leu19, Trp72, Val73, Gly74, Lys79. These residues are located within or adjacent to regions that have been postulated to form beta strands and to be essential to the folding and function of these proteins.
J Mol Neurosci 1992
PMID:Phylogenetically conserved amino acids of MBP and P0 from amphibian myelin. 138 32

We studied the effects of aerosolized DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid (MGTA) (10(-4) M, 90 breaths), a specific inhibitor of carboxypeptidase B-type enzymes, on changes in total pulmonary resistance (RL) induced by aerosolized capsaicin (10(-7) to 10(-4) M; 10 breaths at each concentration) and vagus nerve stimulation (5 V, 5 ms, for 20 s at frequencies varying from 2 to 10 Hz) in anesthetized, atropinized, and ventilated guinea pigs. We also studied the effect of aerosolized MGTA on the bronchoconstrictor response to either aerosolized substance P, neurokinin A (10(-7) to 10(-4) M; 10 breaths at each concentration), and carbachol (10(-5) to 2 x 10(-4) M; 10 breaths at each concentration) or to i.v. administration of neurokinin A (10(-11) to 10(-8) mol/kg), bradykinin (10(-10) to 10(-7) mol/kg), and histamine (10(-8) to 10(-6) mol/kg). Although aerosolized MGTA caused no change in basal RL (P > 0.5), it did potentiate the noncholinergic bronchoconstrictor response to capsaicin (n = 5; P < 0.001) as well as to vagus nerve stimulation (n = 5; P = 0.001). In contrast, MGTA did not potentiate the bronchoconstrictor response to either aerosolized substance P, neurokinin A, and carbachol or to i.v. administration of neurokinin A, histamine, and bradykinin. Carboxypeptidase activity cleaving C-terminal arginine or lysine was found in the membrane preparations of trachea and lung from guinea pigs. The membrane-bound carboxypeptidase activity was maximal at pH 7.0 and was enhanced by the presence of CoCl2 (1 mM) in both the tracheal and lung tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1992 Nov
PMID:Carboxypeptidase M-like enzyme modulates the noncholinergic bronchoconstrictor response in guinea pig. 138 81

An antiserum raised against dehydrin from maize (Zea mays) recognised several polypeptides in extracts of pea (Pisum sativum) cotyledons. A cDNA expression library was prepared from mRNA of developing cotyledons, screened with the antiserum and positive clones were purified and characterised. The nucleotide sequence of one such clone, pPsB12, contained an open reading frame which would encode a polypeptide with regions of significant amino acid sequence similarity to dehydrins from other plant species. The deduced amino acid sequence of the pea dehydrin encoded by B12 is 197 amino acids in length, has a high glycine content (25.9%), lacks tryptophan and is highly hydrophilic. The polypeptide has an estimated molecular mass of 20.4 kDa and pI = 6.4. An in vitro synthesised product from the clone comigrates with one of the in vivo proteins recognised by the antiserum. A comparison of the pea dehydrin sequence with sequences from other species revealed conserved amino acid regions: an N-terminal DEYGNP and a lysine-rich block (KIKEKLPG), both of which are present in two copies. Unexpectedly, pea dehydrin lacks a stretch of serine residues which is conserved in other dehydrins. B12 mRNA and dehydrin proteins accumulated in dehydration-stressed seedlings, associated with elevated levels of endogenous abscisic acid (ABA). Applied ABA induced expression of dehydrins in unstressed seedlings. Dehydrin expression was rapidly reversed when seedlings were removed from the stress or from treatment with ABA and placed in water. During pea cotyledon development, dehydrin mRNA and proteins accumulated in mid to late embryogenesis. Dehydrin proteins were some of the most actively synthesised at about the time of maximum fresh weight and represent about 2% of protein in mature cotyledons.
Plant Mol Biol 1992 Sep
PMID:Pea dehydrins: identification, characterisation and expression. 138 28

Amino acids in the serine proteinase inhibitor eglin c important for its inhibitory specificity and activity have been investigated by site-directed mutagenesis. The specificity of eglin c could be changed from elastase to trypsin inhibition by the point mutation Leu45----Arg (L45R) in position P1 [nomenclature according to Schechter and Berger (1967) Biochem. Biophys. Res. Commun. 27, 157-162]. Model building studies based on the crystal structure of mutant L45R [Heinz et al. (1991) J. Mol. Biol. 217, 353-371] were used to rationalize this specificity change. Surprisingly, the double mutant L45R/D46S was found to be a substrate of trypsin and various other serine proteinases. Multidimensional NMR studies show that wild-type eglin c and the double mutant have virtually identical conformations. In the double mutant L45R/D46S, however, the N-H bond vector of the scissile peptide bond shows a much higher mobility, indicating that the internal rigidity of the binding loop is significantly weakened due to the loss or destabilization of the internal hydrogen bond of the P1' residue. Mutant T44P was constructed to examine the role of a proline in position P2, which is frequently found in serine proteinase inhibitors [Laskowski and Kato (1980) Annu. Rev. Biochem. 49, 593-626]. The mutant remains a potent elastase inhibitor but no longer inhibits subtilisin, which could be explained by model building. Both Arg51 and Arg53, located in the core of the molecule and participating in the hydrogen bonding network with residues in the binding loop to maintain rigidity around the scissile bond, were individually replaced with the shorter but equally charged amino acid lysine. Both mutants showed a decrease in their inhibitory potential. The crystal structure of mutant R53K revealed the loss of two hydrogen bonds between the core and the binding loop of the inhibitor, which are partially restored by a solvent molecule, leading to a decrease in inhibition of elastase by 2 orders of magnitude.
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PMID:Changing the inhibitory specificity and function of the proteinase inhibitor eglin c by site-directed mutagenesis: functional and structural investigation. 139 Jun 62

The importance of amino acid side-chains in helix stability has been investigated by making a series of mutations at the N-caps, C-caps and internal positions of the solvent-exposed faces of the two alpha-helices of barnase. There is a strong positional and context dependence of the effect of a particular amino acid on stability. Correlations have been found that provide insight into the physical basis of helix stabilization. The relative effects of Ala and Gly (or Ser) may be rationalized on the basis of solvent-accessible surface areas: burial of hydrophobic surface stabilizes the protein as does exposure to solvent of unpaired hydrogen bond donors or acceptors in the protein. There is a good correlation between the relative stabilizing effects of Ala and Gly at internal positions with the total change in solvent-accessible hydrophobic surface area of the folded protein on mutation of Ala----Gly. The relationship may be extended to the N and C-caps by including an extra term in hydrophilic surface area for the solvent exposure of the non-intramolecularly hydrogen-bonded main-chain CO, NH or protein side-chain hydrogen bonding groups. The requirement for solvent exposure of the C-cap main-chain CO groups may account for the strong preference for residues having positive phi and psi angles at this position, since this alpha L-conformation results in the largest solvent exposure of the C-terminal CO groups. Glycine in an alpha L-conformation results in the greatest exposure of these CO groups. Further, the side-chains of His, Asn, Arg and Lys may, with positive phi and psi-angles, form a hydrogen bond with the backbone CO of residue in position C -3 (residues are numbered relative to the C-cap). The preferences at the C-cap are Gly much greater than His greater than Asn greater than Arg greater than Lys greater than Ala approximately Ser approximately greater than Asp. The preferences at the N-cap are determined by hydrogen bonding of side-chains or solvent to the exposed backbone NH groups and are: Thr approximately Asp approximately Ser greater than Gly approximately Asn greater than Gln approximately Glu approximately His greater than Ala greater than Val much greater than Pro. These general trends may be obscured when mutation allows another side-chain to become a surrogate cap.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1992 Sep 20
PMID:Alpha-helix stability in proteins. I. Empirical correlations concerning substitution of side-chains at the N and C-caps and the replacement of alanine by glycine or serine at solvent-exposed surfaces. 140 68

Human DNA-PK is a nuclear, serine/threonine protein kinase that, when activated by DNA, phosphorylates several DNA-binding substrates, including the tumor suppressor protein p53. To identify which p53 residues are phosphorylated, we examined DNA-PK's ability to phosphorylate synthetic peptides corresponding to human p53 sequences. Serines 15 and 37 in the amino-terminal transactivation domain of human p53, and serines 7 and 18 of mouse p53, were phosphorylated by DNA-PK in the context of synthetic peptides. Other serines in these p53 peptides, and serines in other p53 peptides, including peptides containing the serine 315 p34cdc2 site and the serine 392 casein kinase II site, were not recognized by DNA-PK or were phosphorylated less efficiently. Phosphorylation of the conserved serine 15 in human p53 peptides depended on the presence of an adjacent glutamine, and phosphorylation was inhibited by the presence of a nearby lysine. Phosphorylation of recombinant wild-type mouse p53 was inhibited at high DNA concentrations, suggesting that DNA-PK may phosphorylate p53 only when both are bound to DNA at nearby sites. Our study suggests that DNA-PK may have a role in regulating cell growth and indicates how phosphorylation of serine 15 in DNA-bound p53 could alter p53 function.
Mol Cell Biol 1992 Nov
PMID:Human DNA-activated protein kinase phosphorylates serines 15 and 37 in the amino-terminal transactivation domain of human p53. 140 79

The functional importance of the two clusters of positively charged amino acids which flank the hydrophobic membrane-anchoring sequence of polyomavirus middle T (mT) protein has been investigated by using site-directed mutagenesis. A clear asymmetry was apparent. No effect on transformation was seen following multiple alterations or complete removal of the cluster at the carboxyl end of the protein. In contrast, a single substitution replacing the first arginine amino terminal to the hydrophobic stretch with glutamic acid, but not with lysine, histidine, or methionine, produced a partially transformation-defective mutant with a novel phenotype. This mutant failed to confer anchorage-independent growth on F111 established rat embryo fibroblasts but induced foci with altered morphology compared with wild-type mT. Biochemical studies on this mutant revealed that F111 clones expressing levels of mutant mT equivalent to those of wild-type controls showed a 65% reduction in pp60c-src activation and an 87% reduction in mT-associated phosphatidylinositol 3-kinase activity. However, F111 clones expressing seven times more mutant mT than did wild-type controls showed equal or greater levels of kinase activities yet remained incompletely transformed. Possible mechanisms involving this transformation-sensitive region of mT are discussed.
Mol Cell Biol 1992 Nov
PMID:Functional asymmetry of the regions juxtaposed to the membrane-binding sequence of polyomavirus middle T antigen. 140 80


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