Abstract
Salmonella typhimurium (official designation Salmonella enterica serovar Typhimurium) is an enteric pathogen and a principal cause of gastroenteritis in humans. A comprehensive description of the proteins of Salmonella and their patterns of expression under different environmental conditions would greatly increase our understanding of the virulence of this organism at the molecular level and provide insights into many other aspects of Salmonella biology. While a variety of two‐dimensional studies of Salmonella have been previously carried out to address specific questions, little systematic information is available at the protein level on the numbers of Salmonella polypeptides that have homologues in other organisms, their abundance, and the frequency of post‐translational modifications. To test the feasibility of determining the proteome of Salmonella, the identities of 53 randomly sequenced cell envelope proteins have been determined by N‐terminal sequencing of spots from two‐dimensional gels. In addition to confirming the existence of previously hypothetical proteins predicted from genomic sequencing projects, we found that approximately 20% of the proteins had no matches in sequence databases. The results suggest that proteome anlysis is an efficient way to identify novel proteins from prokaryotes and that the analysis provides a useful approach to the study of Salmonella virulence.