Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interaction of bacterial polypeptide chain initiation factor 2 (IF-2) with Escherichia coli formylmethionyl-tRNA in the absence of free Mg2+ renders the fMet-tRNA adsorable to nitrocellulose membrane filters. This reaction does not require GTP and is strongly inhibited by low concentration (1 mM) of Mg2+ in the reaction mixture. The structural requirements of the tRNA for binary complex formation have been studied using modified fMet-tRNAfMet molecules and a series of N-blocked and normal aminoacyl-rRNAs. It has been observed that IF-2 will not blind either to free formylmethionine or to a short fMet-oligonucleotide, but will bind to any xRNA structure covalently attached to an N-blocked methionine group. The E. coli initiator and noninitiator methiionine tRNAs, which have many differences in primary structure, were found to bind identically. In addition, fMet-tRNAfMet molecules containing structural modidifications at 20 different sites had the same affinity for IF-2 as unmodified fMet-tRNAfMet. N-blocked eukaryotic initiator tRNAs were also found to bind strongly to the factor. Binary complex formation was readily reversible, f[14C]Met-tRNAfMet being competed out by addition of an equal amount of unlabeled fMet-tRNAfMet to the preformed complex. In contrast, deacylated tRNAfMet was a poor compeitor, a 30-fold excess being required for 50% inhibition of complex formation in the presence of limiting factor. Although tRNAs having an N-blocked methionine were found to have the greatest affinity for IF-2, specificity for the amino acid in binary complex formation was not absolute. Partial binding was observed with N-substituted tyrosine, valine, and phenylalanine tRNAs, and weak or no binding with N-subsituted lysine, alanine, and leucine tRNAs. In all cases, N-blocked derivatives had a higher affinity for IF-2 than the corresponding unsubstituted aminoacyl-tRNAs. These results indicate that IF-2 alone is not capable of distinguishing the nucleotide sequence of tRNAs and selects the initiator tRNA by recognizing the fMet moiety. The overall data suggest that the role of IF-2 in formation of the ribosomal initiation complex is to stablize the interaction of fMet-tRNAfMet with the ribosome at low Mg2+ concentrations by binding to both the ribosomal particle and the fMet group of the tRNA.
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PMID:Interaction of bacterial initiation factor 2 with initiator tRNA. 77 66

A collagenous peptide T1X was isolated from a tryptic digest of the insoluble matrix of calf skin. The peptide consists of two identical polypeptide chains each with a length of 72 amino acid residues joined by a cross-link. Absorption spectra obtained from hydrazone and azine derivatives of T1X indicated that the peptide contains an aldol-type of cross-link (X). The sequence of 23 amino acid residues in the amino-terminal region was determined as Glx-Tyr-Glu-Ala-Tyr-Asp-Val-X-Ser-Gly-Val-Ala-Gly-Gly-Gly-Ile-Ala-Gly-Tyr-Hyp-Gly-Pro-Ala. This sequence overlaps the previously described amino-terminal sequence of alpha1 (III) chain obtained from pepsin treated, insoluble type III collagen. Thus, the present data demonstrate a nonhelical segment of 14 amino acid residues in type III collagen important for cross-linking.
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PMID:Isolation and structure of the amino-terminal cross-linking region in insoluble type III collagen. 79 89

Two classes of spore mutants have been selected in Bacillus cereus T, those producing lysozyme-sensitive spores, and those producing spores dependent upon lysozyme for germination. One mutant from each class was studied in detail and found to have defective packing of the spore coat layers. The major spore coat poplypeptide appeared to be altered on the basis of gel electrophoretic profiles and/or peptide maps of half-syctine-containing peptides. The spores of the mutants of both classes were sensitive to lysozyme and failed to respond to the germinants L-alanine plus adenosine. The spores were also more sensitive to octanol than the parental strain, but contained the same amount of dipicolinic acid and were equally heat resistant. The reversion frequencies in both cases were consistent with an initial point mutation, suggesting that an alteration in the major coat polypeptide accounted for the phenotypic properties studied.
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PMID:Properties of Bacillus cereus spore coat mutants. 80 78

The covalent structure of apolipoprotein A-II, isolated from the serum high-density lipoprotein of a single male Rhesus monkey (Macaca mulatta), was determined. The amino acid sequence of this 77-residue polypeptide is: less than Glu-Ala-Glu-Glu-Pro5-Ser-Val-Glu-Ser-Leu10-Val-Ser-Gln-Tyr-Phe15-Gln-Thr-Val-Thr-Asp20-Tyr-Gly-Lys-Asp-Leu25-Met-Glu-Lys-Val-Lys30-Ser-Pro-Glu-Leu-Gln35-Ala-Gln-Ala-Lys-Ala40-Tyr-Phe-Glu-Lys-Ser45-Lys-Glu-Gln-Leu-Thr50-Pro-Leu-Val-Lys-Lys55-Ala-Gly-Thr-Asp-Leu60-Val-Asn-Phe-Leu-Ser65-Tyr-Phe-Val-Glu-Leu70-Arg-Thr-Gln-Pro-Ala75-Thr-Gln-COOH. A comparison of this structure to that of the monomeric form of human apolipoprotein A-II reveals a high degree of homology except for six conservative amino acid replacements (positions 3, 6, 40, 53, 59, and 71). Of particular structural significance is the replacement of cysteine by serine in position 6. This explaines why Rhesus A-II exists in monomeric form, contrary to the established dimeric nature of the human protein.
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PMID:Covalent structure of apolipoprotein A-II from Macaca mulatta serum high-density lipoproteins. 81 23

Bovine placental lactogen (bPL), a polypeptide hormone functionally related to bovine growth hormone (bGH) and bovine prolactin (bPL), has been isolated from placentas by pH and ammonium sulfate precipitation, gel filtration, and ion exchange chromatography on DEAE- and CM-cellulose. The hormone has been purified to approximately 99% homogeneity, as determined by end group analysis. On disc gel electrophoresis at pH 9.0 bPL migrates as a pair of closely spaced bands (Rf = 09517 and 0.541) between the positions of bGH and bPR. Its molecular weight, as estimated by gel filtration on Sephadex G-200 in 6 M guanidine hydrochloride and 6.5 mM dithiothreitol, is 22, 150 and its isoelectric point is 5.9. The amino acid composition of bPL closely resembles that of bGH and bPR except for a higher content of serine and glycine and a lower leucine content. Like bPR, it has 2 tryptophans and 6 cysteines, but its COOH-terminal sequence is identical with that of bGH: -Cys-Ala-Phe-OH. By Ouchterlony immunodiffusion, bPL forms lines of partial identity with bGH against bGH antisera and with ovine placental lactogen (oPL) against oPL antisera. In the bPL-antibPL system, oPL forms a line of partial identity while bGH and bPR do not cross-react. However, bPL does not form a precipitin line with bPR antisera. These data would indicate that in terms of structure, and hence molecular evolution, bPL and other subprimate placental lactogens occupy a position more intermediate between growth hormone and prolactin than do the primate placental lactogens.
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PMID:Purification and characterization of bovine placental lactogen. 81 97

The sarcoplasmic calcium-binding protein from crayfish muscle has been purified to homogeneity. The protein has a molecular weight of 44000, as determined by sedimentation equilibrium and Sephadex chromatography. It dissociates in the presence of sodium dodecyl sulfate, 8 M urea, or, after succinylation, into two subunits of 22000 molecular weight. The protein is free of carbohydrate and phosphorus but contains 4 g-atoms of calcium/44000 at a free calcium concentration of 0.1 muM. Approximately 45% of the polypeptide backbone appears to be alpha-helical. The amino acid composition reveals a high proportion of alanine and acidic amino acids, a normal content of aromatic amino acids, and the absence of histidine. The isoelectric point, as determined by isoelectric focusing, is 5.1. The protein contains a free threonyl NH2 terminal. Two thiols react rapidly in the native protein, six in the calcium-free form. Immunochemically, there is no difference between the protein from tail, claw, and heart muscle. In these three crayfish tissues, the concentrations of calcium-binding protein, as determined by rocket immunoelectrophoresis, are markedly different: 2.73 g/kg in tail, 0.72 in claw, and 0.073 in heart muscle. A functional analogy with the parvalbumins of vertebrates can be postulated.
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PMID:Isolation and properties of a sarcoplasmic calcium-binding protein from crayfish. 82 Mar 69

The synthetic polypeptide poly-L-(Tyr, Glu)-poly-DL-Ala--poly-L-Lys [(T,G)-A--L] was found to be bound not only by mouse immune serum, but also by nonimmune sera from several species. A combination of immunoelectrophoresis and autoradiography showed that albumin, beta-globulins and immunoglobulins in these sera may bind the antigen. This binding pattern is different, however, for the various species investigated.
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PMID:Binding of (T,G)-A--L by normal sera. 82 36

The activity of pancreatic phospholipase A2 (EC 3.1.1.4) is controlled not only by the architecture of the catalytic site, but is also strongly dependent on the penetrating power of the interface recognition site and the packing density of the lipid-water interface. The influence of the latter two factors on the interface activity has been investigated using chemically modified phospholipases A2 in which the NH2-terminal L-Ala8 has been replaced by DL-[3-13C]Ala, or in which the polypeptide chain has been elongated with DL-[3-13C]Ala. The [DL-(3-13C)Ala8]phospholipase A2 could be resolved into the pure diastereoisomers, [D-(3-13C)Ala8]phospholipase A2 and [L-(3-13C)Ala8]phospholipase A2 by elution on Sephadex G-100 in the presence of a micellar lipid-water interface, as well as by conventional ion exchange chromatography on carboxymethylcellulose. Similar procedures did not effect, however, a separation of DL-[3-13C]Ala7-phospholipase A2 into their respective diasteroisomers, indicating the strategic role of the NH2-terminal L-Ala8 residue in the interaction process between the enzyme and lipid-water interfaces. Kinetic experiments using various micellar short chain lecithins revealed the apparent absence of an interface recognition site in [D-(3-13C)Ala8]- and DL-[3-13C]Ala7-phospholipase A2, while these proteins still possess considerable enzymatic activity toward monomeric substrates. In contrast, however, kinetic experiments using monomolecular surface films, allowing a continuous change in surface density of the substrate molecules, revealed that [D-(3-13C)Ala8]- and DL-[3-13C]Ala7-phospholipase A2 at low surface pressure possess about 60 and 30% of the interface activity of native phospholipase A2, respectively. These results therefore suggest that the modified phospholipases A2 do possess an interface recognition site although less powerful as compared to that of the native enzyme, enabling the estimation of the surface density of micellar short chain lecithins.
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PMID:Regulation of phospholipase A2 activity by different lipid-water interfaces. 85 38

Factor XII was purified approximately 14 000-fold from bovine plasma by ammonium sulfate fractionation followed by heparin-agarose, DEAE-Sephadex, CM-cellulose, arginine-agarose, and benzamidine-agarose column chromatography. By this method, about 15 mg of protein was purified from 15 L of plasma with an overall yield of 18%. The purified protein was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino-terminal analysis. Bovine factor XII is a glycoprotein with a mol wt of 74 000 as determined by sedimentation equilibrium centrifugation. It contains 13.5% carbohydrate including 3.4% hexose, 4.7% N-acetylhexosamine, and 5.4% N-acetylneuraminic acid. Factor XII is a single polypeptide chain with an NH2-terminal sequence of Thr-Pro-Pro-Trp-Lys-Gly-Pro-?-Lys-His. This sequence is homologous to the reactive-site regions of a number of protease inhibitors. The amino acid sequence of a carboxyl-terminal fragments prepared by cyanogen bromide digestion was found to be Leu-Cys-Ala-Gly-Phe-Leu-Glu-Gly-Gly-Thr-Asp-Ala-Cys-Gln-Gly-Asp-SER-Gly-Gly-Pro-Leu-Val-Cys-Glu-Asp-Glu. This sequence is homologous with the active site of a number of plasma serine proteases including thrombin, factor IXa, factor Xa, and plasmin. These data indicate that bovine factor XII is a precursor to a serine enzyme with an inhibitor sequence and a catalytic site located in the same single polypeptide chain.
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PMID:Isolation and characterization of bovine factor XII (Hageman factor). 86 Dec 10

Rotational isomeric state theory, in the form appropriate for branched molecules, has been used to calculate the mean-square unperturbed radius of gyration, (s2)0, for cross-linked polyglycine, poly(L-alanine), poly(L-proline), poly(L-alanyl-D-alanine), poly(L-propyl-L-prolylglycine), poly(L-prolyl-L-alanylglycine, poly(glycyl-L-alanyl-L-proline), and poly(L-alanyl-L-alanylglycine). The central amino acid residue in each polypeptide chain is replaced by the L-cysteinyl residue involved in cross-link formation. Each cross-linked molecular is considered to contain two trifunctional branch points, the alpha-carbon atoms of the two L-cysteinyl residues. Random flight statistics provide a poor estimate for g, defined as the ratio of (s2)0 for branched and linear polypeptides containing the same number of amino acid residues, for molecules of moderate molecular weight. The values of g obtained by random flight statistics and rotational isomeric state theory merge as the molecular weight becomes infinite. Deviations of g from its random flight value correlate with the size of the characteristic ratio, (s2)0/nplp2, for the linear polypeptides. The number of peptide bonds is np, and lp denotes the distance between neighboring alpha carbon atoms. Random flight statistics perform better in estimating the change in (s2)0 accompanying the cross-linking of the two polypeptide chains than it does in the estimation of g.
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PMID:Unperturbed dimensions for homopolypeptides and sequential copolypeptides cross-linked via a disulfide bond. 88 85


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