Research Article
Ying Jiang, Quanjun Wang, J
Abstract
Constitutively phosphorylated proteins in Human fetal liver (HFL) aged 16-24 wk of gestation were studied using a 2-DE step followed by western blotting detection and MS identification. We found 166 phosphorylated protein spots with quantitative information and identified 101 gene products. Of theses identified proteins, 57 contain phosphoserine, 49 contain phosphothreonine, 51 contain phosphotyrosine, and 64 were newly identified phosphorylated proteins. The possible phosphorylation sites were further predicted using Netphos, ScanProsite and Scansite programs and most proteins were predicted the same site by at least 2 programs. Integrating the functional categories, protein abundance and the degree of phosphorylation of these proteins, we found proteins related to carbohydrate, lipid and amino acid metabolism were highly expressed with also the high degree of all serine, threonine and tyrosine phosphorylation; proteins associated with hematopoiesis were relatively highly expressed but with a relatively low degree of phosphorylation at serine, threonine and tyrosine; the proteins for signal transduction; biosynthesis of secondary metabolites and those whose function were unknown were lowly expressed, but with the zhigh degree of phosphorylation and interestingly, serine was the main phosphorylated amino acid of signal transducers; threonine in enzymes of biosynthesis of secondary metabolites; and tyrosine in proteins with unknown function.