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1.
Hemoglobins in sheep: multiple differences in amino acid sequences of three beta-chains and possible origins 总被引：6，自引：0，他引：6
S H Boyer P Hathaway F Pascasio C Orton J Bordley M A Naughton 《Science (New York, N.Y.)》1966,153(743):1539-1543
Among the three adult sheep hemoglobins (A, B, and C), two (A and B) are reportedly products of alleles. The beta-chains of A and B differ by at least seven scattered amino acid residues whereas the beta-sequence of C differs from A by at least 16 residues and from B by at least 21 residues. These changes suggest that the origin of C-beta antedated the divergence of A and B. Five shared differences between A-beta and C-beta with respect to B-beta can be interpreted as the result of selective advantage in favor of B. A complex of additional mechanisms has possibly been involved in maintaining the A-B- C porymorphism. 相似文献
2.
T Miyaji Y Oba K Yamamoto S Shibata I Iuchi H B Hamilton 《Science (New York, N.Y.)》1968,159(811):204-206
A variant of hemoglobin A, named Hb Hijiyama, found in two generations of a Japanese family living in Hiroshima, Japan, has a higher anodal electrophoretic mobility than hemoglobin A; a gain of two negative charges per molecule is indicated. Fingerprinting and amino acid analysis showed the biochemical anomaly to be in the beta chain at residue 120, where lysine is replaced by glutamic acid. In the heterozygote carriers of the abnormal hemoglobin there is no apparent association with clinical or hematologic abnormalities. 相似文献
3.
Stamatoyannopoulos G Yoshida A Adamson J Heinenberg S 《Science (New York, N.Y.)》1968,159(3816):741-743
Hemoglobin Rainier, a new hemoglobin variant associated with erythrocytosis, was found in six members of a Caucasiant family. Structurally, it represents substitution of histidine for the invariant residute H23 tyrosine in the beta-hemoglobin polypeptide chain (beta(145) tyrosine --> histidine). Hemoglobin Rainier is the first example of a single amino acid substitution in adult human hemoglobin, causing increased resistance to alkali denaturation. 相似文献
4.
The mechanism of alkali resistance in hemoglobin Rainier, an adult human hemoglobin variant (beta 145 tyrosinie --> histidinie), has been investigated. Alkali denaturation kinetics, electrophoretic and hybridization study. and ultracentrifuge analysis provided evidence for a monomeric beta Rainiier chain resisting denaturation at alkaline pH. These data provide evidence for a previously unrecognized effect of a single amino acid substitution, that is, the change of the alkali denaturation properties of monomneric chains. 相似文献
5.
Hemoglobin G Taegu, an electrophoretically slow hemoglobin with a structural anomaly believed to be in the beta-T-3 section of the beta chain, was the only variant found among 6700 normal Koreans. Four subjects, 0.06 percent, had the G-hemoglobin variant in addition to normal hemoglobin A. Hemoglobin E, known in numerous groups from Southeast Asia and the variant most frequently seen in Chinese subjects, was not found among the Koreans we tested. 相似文献
6.
Hemoglobin Freiburg: abnormal hemoglobin due to deletion of a single amino acid residue 总被引：5，自引：0，他引：5
R T Jones B Brimhall T H Huisman E Kleihauer K Betke 《Science (New York, N.Y.)》1966,154(752):1024-1027
Structural characterization of a new variant of human hemoglobin (adult), designated hemoglobin Freiburg, indicates the deletion of the valyl residue No. 23 from an otherwise normal beta-chain. The formula may be written (alpha2)beta(2)(23val-0). The abnormal hemoglobin is present with hemoglobin A in the proposita and in two of her three living children, but is not detectable in her parents. We postulate that this variant represents a triplet base deletion which most likely resulted from an unequal crossing-over between two normal betachain loci during meiosis in one of the parents of the proposita. 相似文献
7.
Erythrocyte metabolism: interaction with oxygen transport 总被引：4，自引：0，他引：4
Studies of the interactions between the metabolism and the function of the red cell have shown the importance of the red cell's metabolism in contributing to the maintenance of adequate oxygen delivery. Some of the phosphorylated intermediates of glycolysis, especially DPG, are now known to reduce the affinity of hemoglobin for oxygen. Current evidence indicates that this phenomenon is due to the effects of the binding of DPG to the , beta-chains of deoxyhemoglobin. It appears that increases in red cell concentrations of DPG commonly occur during hypoxia, and that these increases (as well as normal physiological variation) significantly enhance oxygen transport. Artificial manipulation of erythrocyte metabolism may soon prove to be of great clinical usefulness in the treatment of a great variety of disorders which limit oxygen transport. 相似文献
8.
Examination of the amino acid sequences of human cytochrome c and the alpha-chain variant of human hemoglobin Constant Spring has revealed the possiblity for base-paired hairpin loops in the messenger RNA's for these proteins. A similar analysis of the bacteriophage R17 coat protein suggests an additional unobserved loop in the R17 RNA. If such loops are present in messenger RNA's generally, it would suggest that DNA has more than one stable base-paired conformation. 相似文献
9.
Globin composition and synthesis of hemoglobins in developing fetal mice erythroid cells 总被引：24，自引：0，他引：24
Fetal mouse erythropoiesis proceeds initially in yolk-sac blood islands (8 to 12 days) and, subsequently, in liver (12 to at least 16 days). Yolksac cells synthesize three hemoglobins, Hb E(I), Hb E(II) and Hb E(III). Hb E(I) has x- and y-globin chains; Hb E(II) has alpha and y; HB E(III), alpha and z. No detectable beta-globin is formed in these cells. Liver erythroid cells form only adult hemoglobin, composed of alpha- and beta-chains. 相似文献
10.
T-cell recognition of Ia molecules selectively altered by a single amino acid substitution 总被引：5，自引：0，他引：5
M A Brown L A Glimcher E A Nielsen W E Paul R N Germain 《Science (New York, N.Y.)》1986,231(4735):255-258
T lymphocytes recognize foreign antigen together with allele-specific determinants on membrane-bound class I and class II (Ia) gene products of the major histocompatibility complex. To identify amino acids of class II molecules critical to this recognition process, the genes encoding the beta chains of the I-Ak molecule were cloned from a wild-type B-cell hybridoma and from an immunoselected variant subline showing distinct serological and T-cell stimulatory properties. Nucleotide sequencing and DNA-mediated gene transfer established that a single base transition (G----A) encoding a change from glutamic acid to lysine at position 67 in the I-Ak beta molecule accounted for all the observed phenotypic changes of the variant cells. These results confirm the importance of residues 62 to 78 in the amino terminal domain of I-A beta for class II-restricted T-cell recognition of antigen and demonstrate the ability of a single substitution in this region to alter this recognition event. 相似文献
11.
Interaction properties of tropocollagen are markedly altered by treatment with pepsin. This treatment liberates terminal or near-terminal covalently bonded peptides whose amino acid composition is strikingly different from the composition of the pepsin-resistant triple-helix body of the macromolecule. Pepsin also converts most of the beta-chains to alpha-chains. This fact indicates that the interchain link is also external to the body of the macromolecule and probably involves peptides. The role of these properties in bioregulative mechanisms is briefly discussed. 相似文献
12.
Restoration of inactivation in mutants of Shaker potassium channels by a peptide derived from ShB 总被引：51，自引：0，他引：51
Site-directed mutagenesis experiments have suggested a model for the inactivation mechanism of Shaker potassium channels from Drosophila melanogaster. In this model, the first 20 amino acids form a cytoplasmic domain that interacts with the open channel to cause inactivation. The model was tested by the internal application of a synthetic peptide, with the sequence of the first 20 residues of the ShB alternatively spliced variant, to noninactivating mutant channels expressed in Xenopus oocytes. The peptide restored inactivation in a concentration-dependent manner. Like normal inactivation, peptide-induced inactivation was not noticeably voltage-dependent. Trypsin-treated peptide and peptides with sequences derived from the first 20 residues of noninactivating mutants did not restore inactivation. These results support the proposal that inactivation occurs by a cytoplasmic domain that occludes the ion-conducting pore of the channel. 相似文献
13.
Phenylhydrazine-induced anemia in the domestic cat results in an increase in minor, high oxygen affinity hemoglobin B components and an accompanying decrease in the major, low affinity B component. This change is accompanied by an unusually large increase in erythrocytic adenosine triphosphate and 2,3-diphosphoglycerate, a slight decrease in the oxygen affinity of whole blood, and a large decrease in the Hill constant. 相似文献
14.
The glycosylation of hemoglobin: relevance to diabetes mellitus 总被引：34，自引：0，他引：34
Glucose reacts nonenzymatically with the NH2-terminal amino acid of the beta chain of human hemoglobin by way of a ketoamine linkage, resulting in the formation of hemoglobin AIc. Other minor components appear to be adducts of glucose 6-phosphate and fructose 1,6-diphosphate. These hemoglobins are formed slowly and continuously throughout the 120-day life-span of the red cell. There is a two- to threefold increase in hemoglobin AIc in the red cells of patients with diabetes mellitus. By providing an integrated measurement of blood glucose, hemoglobin AIc is useful in assessing the degree of diabetic control. Furthermore, this hemoglobin is a useful model of nonenzymatic glycosylation of other proteins that may be involved in the long-term complications of the disease. 相似文献
15.
The amount of acceptance of each amino acid per absorbancy unit of rabbit reticulocyte transfer RNA was determined. The results were compared with the amino acid composition of rabbit hemoglobin and with a similar determination of the transfer RNA content of rabbit liver. The histidine and isoleucine transfer RNA content of reticulocytes is specialized for the synthesis of hemoglobin, in which histidine is unusually common and isoleucine unusually scarce compared to most proteins. 相似文献
16.
Hidden thermodynamics of mutant proteins: a molecular dynamics analysis 总被引：13，自引：0，他引：13
A molecular dynamics simulation method is used to determine the contributions of individual amino acid residues and solvent molecules to free energy changes in proteins. Its application to the hemoglobin interface mutant Asp G1(99) beta----Ala shows that some of the contributions to the difference in the free energy of cooperativity are as large as 60 kilocalories (kcal) per mole. Since the overall free energy change is only -5.5 kcal/mole (versus the experimental value of -3.4 kcal/mole), essential elements of the thermodynamics are hidden in the measured results. By exposing the individual contributions, the free energy simulation provides new insights into the origin of thermodynamic changes in mutant proteins and demonstrates the role of effects beyond those usually considered in structural analyses. 相似文献
17.
本文利用从日本引进的大豆品系LA与国内品种（系）杂交后代中选出的8个大豆。7s球蛋白变异品系，进行了各品质性状的方差分析和相关分析。方差分析结果表明：7s球蛋白变异品系的胱氨酸含量、含硫氨基酸（蛋＋胱）含量极显著高于对照（吉林20）。相关分析结果表明：17种氨基酸中10种氨基酸与蛋白质含量为显著或极显著正相关；蛋白质与脂肪含量间为极显著负相关；胱氨酸与蛋氨酸相关不显著；胱氨酸与蛋白质为极显著正相关，与其他各氨基酸呈不同程度的正相关；蛋氨酸与蛋白质以及各氨基酸间的相关均不显著。就利用7s球蛋白变异特性来提高大豆籽粒含硫氨基酸含量而言，其含硫氨基酸提高效果显著，而含硫氨基酸含量的提高不会带来蛋白质和其他氨基酸含量下降的负作用。利用7s球蛋白变异特性，可以培育出含硫氨基酸、蛋白质含量都高的双高品种。 相似文献
18.
A new cofactor in a prokaryotic enzyme: tryptophan tryptophylquinone as the redox prosthetic group in methylamine dehydrogenase 总被引：12，自引：0，他引：12
W S McIntire D E Wemmer A Chistoserdov M E Lidstrom 《Science (New York, N.Y.)》1991,252(5007):817-824
Methylamine dehydrogenase (MADH), an alpha 2 beta 2 enzyme from numerous methylotrophic soil bacteria, contains a novel quinonoid redox prosthetic group that is covalently bound to its small beta subunit through two amino acyl residues. A comparison of the amino acid sequence deduced from the gene sequence of the small subunit for the enzyme from Methylobacterium extorquens AM1 with the published amino acid sequence obtained by the Edman degradation method, allowed the identification of the amino acyl constituents of the cofactor as two tryptophyl residues. This information was crucial for interpreting 1H and 13C nuclear magnetic resonance, and mass spectral data collected for the semicarbazide- and carboxymethyl-derivatized bis(tripeptidyl)-cofactor of MADH from bacterium W3A1. The cofactor is composed of two cross-linked tryptophyl residues. Although there are many possible isomers, only one is consistent with all the data: The first tryptophyl residue in the peptide sequence exists as an indole-6,7-dione, and is attached at its 4 position to the 2 position of the second, otherwise unmodified, indole side group. Contrary to earlier reports, the cofactor of MADH is not 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), a derivative thereof, or pro-PQQ. This appears to be the only example of two cross-linked, modified amino acyl residues having a functional role in the active site of an enzyme, in the absence of other cofactors or metal ions. 相似文献
19.
对玉米ＤＮＡ导入水稻后代变异系的种子组分的分析结果表明，与受体相比，直链淀粉含量存在明显差异，清蛋白、球蛋白和谷蛋白比例均发生了变异。氨基酸组分中以极性氨基酸组分变异较大，特别是酸性和碱性氨基酸组分均发生了明显变异。 相似文献
20.
Tryptophan deficiency in rabbit reticulocytes: polyribosomes during interrupted growth of hemoglobin chains 总被引：9，自引：0，他引：9
Of several amino acids essential for optimum hemoglobin synthesis by the rabbit reticulocyte, only omission of tryptophan results in polyribosome disaggregation. This disaggregation is prevented by the omission of both tryptophan and an amino acid that is relatively more essential than tryptophan for hemoglobin synthesis. Since tryptophan is located only near the amino-terminal ends of both chains of rabbit globin, the results indicate that single ribosomes and those in polyribosomes are in a dynamic state in the intact cell. 相似文献