title: Purification, characterization and nucleotide sequence of the periplasmic C4-dicarboxylate-binding protein (DctP) from Rhodobacter capsulatus.
abstract: A periplasmic binding protein essential for high-affinity transport of the C4-dicarboxylates malate, succinate and fumarate across the cytoplasmic membrane of the purple photosynthetic bacterium Rhodobacter capsulatus has been purified to homogeneity and some of its ligand-binding properties characterized. The protein was not produced in a Tn5 insertion mutant unable to transport C4-dicarboxylates under aerobic conditions in the dark. Wild-type DNA corresponding to the location of the transposon insertion site was subcloned and a 1.5 kb section sequenced. A complete open reading frame of 999 bp was identified that encoded a 333-residue protein (DctP) with a molecular weight of 36,128 with a 26-residue amino-terminal signal peptide. The identify of this protein with the purified dicarboxylate-binding protein and the position of the predicted signal peptide cleavage site was confirmed by N-terminal sequencing. No significant homology with other proteins was detected in database searches. A GC-rich region of dyad symmetry was located 7 bp downstream of the dctP translational stop codon. This structure may be of significance in regulating the relative abundance of DctP and other dct gene products which comprise the high-affinity dicarboxylate transport system in this bacterium.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, U.K.
authors.forename: J G
authors.initials: JG
authors.lastname: Shaw
authors.forename: M J
authors.initials: MJ
authors.lastname: Hamblin
authors.forename: D J
authors.initials: DJ
authors.lastname: Kelly
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000235:genetics*; D002462:Cell Membrane / Q000737:chemistry*; D003001:Cloning, Molecular; D029382:Dicarboxylic Acid Transporters; D005650:Fumarates / Q000378:metabolism; D007700:Kinetics; D008293:Malates / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D016354:Rhodobacter capsulatus / Q000235:genetics*; D013386:Succinates / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029382:Dicarboxylic Acid Transporters; D005650:Fumarates; D008293:Malates; D008565:Membrane Proteins; D013386:Succinates; C074174:DctP protein, Rhodobacter capsulatus