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131.
132.
S B Sheren E F Eikenberry D L Broek M van der Rest T Doering J Kelly T Hardt B Brodsky 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,85(1):5-14
The major collagen in lamprey notochord is type II, as determined by its amino acid composition and solubility properties. This collagen has a distribution of charged residues indistinguishable from higher vertebrate Type II collagens as judged by its SLS banding pattern. Lamprey type II collagen has a higher thermal stability than lamprey skin collagen, in contrast to the identical melting temperatures for these types in mammals. A minor collagen in lamprey notochord has solubility properties, amino acid composition, and electrophoretic mobility similar to that of 1 alpha, 2 alpha, 3 alpha collagen in human cartilage. 相似文献
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Joseph W Brown Joshua S Rest Jaime García-Moreno Michael D Sorenson David P Mindell 《BMC biology》2008,6(1):6
Background
Determining an absolute timescale for avian evolutionary history has proven contentious. The two sources of information available, paleontological data and inference from extant molecular genetic sequences (colloquially, 'rocks' and 'clocks'), have appeared irreconcilable; the fossil record supports a Cenozoic origin for most modern lineages, whereas molecular genetic estimates suggest that these same lineages originated deep within the Cretaceous and survived the K-Pg (Cretaceous-Paleogene; formerly Cretaceous-Tertiary or K-T) mass-extinction event. These two sources of data therefore appear to support fundamentally different models of avian evolution. The paradox has been speculated to reflect deficiencies in the fossil record, unrecognized biases in the treatment of genetic data or both. Here we attempt to explore uncertainty and limit bias entering into molecular divergence time estimates through: (i) improved taxon (n = 135) and character (n = 4594 bp mtDNA) sampling; (ii) inclusion of multiple cladistically tested internal fossil calibration points (n = 18); (iii) correction for lineage-specific rate heterogeneity using a variety of methods (n = 5); (iv) accommodation of uncertainty in tree topology; and (v) testing for possible effects of episodic evolution. 相似文献135.
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Cartilage type IX collagen-proteoglycan contains a large amino-terminal globular domain encoded by multiple exons 总被引:7,自引:0,他引:7
G Vasios I Nishimura H Konomi M van der Rest Y Ninomiya B R Olsen 《The Journal of biological chemistry》1988,263(5):2324-2329
Type IX collagen in cartilage consists of molecules composed of three genetically distinct polypeptide subunits. One of the subunits, alpha 2(IX), contains a covalently attached glycosaminoglycan side chain whereas a second subunit, alpha 1(IX), contains a large noncollagenous, amino-terminal domain called NC4. In this report, we describe for the first time the complete primary structure of this noncollagenous domain, based on cloning and sequencing of cDNA and genomic DNA as well as amino acid sequencing of tryptic peptides. Analysis of genomic clones has also allowed determination of the exon structure of NC4. Our results demonstrate that the noncollagenous, amino-terminal domain of alpha 1(IX) chains contains 266 amino acid residues (including the signal peptide) with 5 cysteinyl residues forming two disulfide bridges. The domain is basic with an estimated pI of 9.7, thus supporting the idea that it may participate in ionic interactions with polyanionic glycosaminoglycans in cartilage. Both the sequence and exon structure of the NC4 domain is unique among collagens and there is no obvious homology with the noncollagenous domains of other types of collagen, including the propeptides of fibrillar collagens. 相似文献
138.
Secondary transporters for citrate and the Mg(2+)-citrate complex in Bacillus subtilis are homologous proteins. 下载免费PDF全文
Citrate uptake in Bacillus subtilis is mediated by a secondary transporter that transports the complex of citrate and divalent metal ions. The gene coding for the transporter termed CitM was cloned, sequenced, and functionally expressed in Escherichia coli. Translation of the base sequence to the primary sequence revealed a transporter that is not homologous to any known secondary transporter. However, CitM shares 60% sequence identity with the gene product of open reading frame N15CR that is on the genome of B. subtilis and for which no function is known. The hydropathy profiles of the primary sequences of CitM and the unknown gene product are very similar, and secondary structure prediction algorithms predict 12 transmembrane-spanning segments for both proteins. Open reading frame N15CR was cloned and expressed in E. coli and was shown to be a citrate transporter as well. The transporter is termed CitH. A remarkable difference between the two transporters is that citrate uptake by CitM is stimulated by the presence of Mg2+ ions, while citrate uptake by CitH is inhibited by Mg2+. It is concluded that the substrate of CitM is the Mg(2+)-citrate complex and that CitH transports the free citrate anion. Uptake experiments in right-side-out membrane vesicles derived from E. coli cells expressing either CitM or CitH showed that both transporters catalyze electrogenic proton/substrate symport. 相似文献
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Stephen J. Hadfield Justin A. Pachebat Martin T. Swain Guy Robinson Simon JS Cameron Jenna Alexander Matthew J. Hegarty Kristin Elwin Rachel M. Chalmers 《BMC genomics》2015,16(1)