Structure and evolution of the human genes encoding protein C and coagulation factor IX

✍ Scribed by George L. Long

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 356 KB
• Volume: 33
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240330305

✦ Synopsis

Human protein C is a vitamin K-dependent plasma protein that serves as a feedback down-regulator of the coagulation cascade by specifically degrading the protein cofactors VIIIa and Va. The protein C precursor consists of the following domains: leader peptide, "gla" region, two epidermal growth factor segments, and the activation peptide/serine protease. Comparison of amino acid sequences reveals that protein C and factor IX are homologous. A comparison of the genes for protein C and factor IX shows that all seven of the introns within the protein coding regions are in identical positions and correspond to protein structurefunction domain boundries. However, the base compositions of the two genes (coding and noncoding regions) are remarkably different: -60% guanine + cytosine (G + C) for protein C versus -40% G + C for factor IX. One possible explanation for this phenomenon is that the factor IX gene (located on the X chromosome) has undergone extensive deoxycytosine methylation and subsequent spontaneous deamination mutagenesis, resulting in a net C to thymine (and G to adenine) transition. This would suggest that the protein C gene may represent a more primitive form of the gene duplication precursor.