Analysis of the membrane proteins in human serum

Abstract

Serum and membrane proteins are two of the most attractive targets for proteomic analysis. Previous membrane protein studies tend to focus on tissue samples, while researches on membrane proteins in serum are still limited. In this study, human albumin and IgG depleted sera have been used for the proteome separation by SDS-PAGE. After staining, gels with protein fractions were cut and digested by trypsin. The peptide mixtures extracted from each gel slice were analyzed by nano-liquid chromatography-electrospray ionization mass spectrometry (NanoLCESI- MS/MS). The proteins were identified by Mascot v1.8 software and validated by MSQuant v1.5 software. As the result, a database including 1,216 membrane proteins, of which 469 (38.6%) membrane proteins with at least one transmembrane domain (TMD) were identified based on three different transmembrane prediction applications (Phobius, TMHMM, and SOSUI), was established. These proteins were further characterized and classified into different functional categories, such as cellular component, molecular function and biological process, based on their role according to Gene Ontology. Our results suggest that membrane proteomics will allow more pathway study related to diseases and will enable a better understanding of drug targets. © 2013 Dan PD, et al.