Partial mRNA sequences for human A alpha, B beta, and gamma fibrinogen chains: evolutionary and functional implications.
Using rat cDNA and genomic probes to screen a human liver cDNA library, we have isolated clone of 2,274, 855, and 736 base pairs (bp) coding for the A alpha, B beta and gamma chains of human fibrinogen. Sequence analysis reveals a hitherto unrecognized extension of 15 amino acids at the carboxyl terminus of the A alpha chain, the terminal residue of which is proline. This brings the known length of the human A alpha chain to 625 amino acids. The 13-amino-acid repeated region in the midportion of the A alpha chain clearly has arisen through an 8-fold duplication of a 39-bp genetic element, which itself appears to have been constructed from smaller 6-bp repeating units. Greater than 50% sequence homology between B beta- and gamma-chain coding regions confirms postulates that these genes have arisen by duplication and subsequent divergence of an ancestral gene. A comparison of human and rat gamma-chain cDNAs shows more than 88% sequence homology over the carboxyl-terminal 162 amino acids, implying strong selective pressures on these portions of the gamma-chain gene.
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis*; D005340:Fibrinogen / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008099:Liver / Q000201:enzymology; D046911:Macromolecular Substances; D010957:Plasmids; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D013045:Species Specificity
D046911:Macromolecular Substances; D012333:RNA, Messenger; D005340:Fibrinogen; D004247:DNA