Downloaded from www.microbiologyresearch.org by IP: 54.162.190.106 On: Fri, 11 Mar 2016 02:59:37 Microbiology (1995), 141, 961-971 Printed in Great Britain Novel phosphotransferase system genes revealed by bacterial genome analysis - a gene cluster encoding a unique Enzyme I and the proteins of a fructose-like permease system Jonathan Reizer, Aiala Reizer and Milton H. Saier, Jr Author for correspondence: Milton H. Saier, Jr. Tel: + 1 619 534 4084. Fax: + 1 619 534 7108. e-mail : msaier @ucsd.edu Department of Biology, University of California at San Diego, La Jolla, CA 92093-01 16, USA Previous publications have demonstrated the presence of a cryptic gene encoding a novel Enzyme I of the phosphoeno1pyruvate:sugar phosphotransferase system (PTS). Recent Escherichia coli genome sequencing revealed a gene (ptsA) encoding a new Enzyme I homologue in the 89.1-89.3 centisome region. We have analysed this region, and here describe and characterize open reading frames (ORFs) encoding (1) a fused PTS Enzyme I- llAFN homologue, (2) a glycerol dehydrogenase, (3) a transaldolase homologue, (4) two PTS llBFN homologues, (5) a PTS IICFw homologue, and (6) homologues of pyruvate formate-lyase and its activating enzyme. Binary comparison scores, multiple alignments and phylogenetic trees establish the families of proteins to which each of the relevant ORFs belong. Identification of the putative products of this gene cluster leads to the proposal that several of the proteins encoded in this region function in anaerobic carbon metabolism. Keywords : sugar transport, phosphotransferase system, anaerobiosis, glycerol dehydrogenase, pyruvate formate-lyase INTRODUCTION Bacteria take up and concomitantly phosphorylate sugars via a phosphoenolpyruvate: sugar phosphotransferase system (Postma et al., 1993). This system transports dozens of sugars via a chain of phosphoryl transfer proteins that consists of two non-sugar-specific com- ponents, Enzyme I (I) and HPr, and three or four protein domains of the sugar-specific Enzyme I1 complex (En- zymes or domains IIA, IIB, IIC and sometimes IID) (Saier & Reizer, 1992). The phosphoryl transfer chain of the PTS, regardless of the sugar transported, is as follows : PEP + I + HPr + IIA + IIB -+ sugar Of these proteins or protein domains, only the IIC component, the sugar recognition constituent that trans- ports the sugar, is not phosphorylated. IIA and IIB are cytoplasmic proteins or peripherally IIC Abbreviations: PEP, phosphoenolpyruvate; PTS, phosphotransferase sys- tem. membrane-associated domains of the Enzyme I1 complex, and IIC is an integral membrane permease. The phylo- genies of these protein domains have been characterized in previous publications (Reizer et al., 1991b; Saier et al., 1992; Saier & Reizer, 1992, 199413). The characterized fructose-specific and fructose-like Enzyme I1 complexes exhibit IIA and IIB domains that resemble those of the mannitol-specific Enzyme I1 complex, but the IIC domains are more divergent (see Reizer et al., 1994a). In 1987 we published results showing that strains of Salmonella gphimt/rit/m that were deleted for the pts genes encoding Enzyme I and HPr could be mutated so as to regain PTS function (Chin et al., 1987). A novel Enzyme I was identified and partially characterized, and it proved to have catalytic properties similar to those of the deleted Enzyme I (S. Sutrina, J. Reizer & M. H. Saier, Jr, unpublished results). The gene, designated ptsj, which when mutated gave rise to expression of this novel Enzyme I appears to encode a transcriptional regulatory protein within the GntR family (Reizer et al., 1991a; Titgemeyer et al., 1994). Recent operon and genome sequence analyses in Escheri- 0001-9344 0 1995 SGM 96 1