Open AccessMembrane Topology of PssT, the Transmembrane Protein Component of the Type I Exopolysaccharide Transport System in Rhizobium leguminosarum bv. trifolii Strain TA1
Author(s) -
Andrzej Mazur,
Jarosław Król,
Małgorzata Marczak,
Anna Skorupska
Publication year - 2003
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.185.8.2503-2511.2003
Subject(s) - biology , mutant , rhizobium leguminosarum , transmembrane protein , transmembrane domain , rhizobiaceae , gene , amino acid , genetics , biochemistry , bacteria , symbiosis , receptor
The pssT gene was identified as the fourth gene located upstream of the pssNOP gene cluster possibly involved in the biosynthesis, polymerization, and transport of exopolysaccharide (EPS) in Rhizobium leguminosarum bv. trifolii strain TA1. The hydropathy profile and homology searches indicated that PssT belongs to the polysaccharide-specific transport family of proteins, a component of the type I system of the polysaccharide transport. The predicted membrane topology of the PssT protein was examined with a series of PssT-PhoA fusion proteins and a complementary set of PssT-LacZ fusions. The results generally support a predicted topological model for PssT consisting of 12 transmembrane segments, with amino and carboxyl termini located in the cytoplasm. A mutant lacking the C-terminal part of PssT produced increased amounts of total EPS with an altered distribution of high- and low-molecular-weight forms in comparison to the wild-type RtTA1 strain. The PssT mutant produced an increased number of nitrogen fixing nodules on clover.