Sequence and structural similarities between the leucine-specific binding protein and leucyl-tRNA synthetase of Escherichia coli.
A role for the leucyl-tRNA synthetase (EC 6.1.1.4) has been established for regulating the transport of leucine across the inner membrane of Escherichia coli by the leucine, isoleucine, valine (LIV-I) transport system. This transport system is mediated by interactions of periplasmic binding proteins with a complex of membrane-associated proteins, and transcription of the high-affinity branched-chain amino acid transport system genes is repressed by growth of E. coli on high levels of leucine. We now report results from sequence comparisons and structural modeling studies, which indicate that the leucine-specific binding protein, one of the periplasmic components of the LIV-I transport system, contains a 121-residue stretch, representing 36% of the mature protein, which displays both sequence and structural similarities to a region within the putative nucleotide-binding domain of leucyl-tRNA synthetase. Early fusion events between ancestral genes for the leucine-specific binding protein and leucyl-tRNA synthetase could account for the similarity and suggest that processes of aminoacylation and transport for leucine in E. coli may be performed by evolutionarily interrelated proteins.
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606.
R M
RM
Williamson
D L
DL
Oxender
D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics*; D005075:Biological Evolution; D002352:Carrier Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007930:Leucine / Q000378:metabolism*; D007935:Leucine-tRNA Ligase / Q000235:genetics*; D008961:Models, Structural; D008969:Molecular Sequence Data; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid
D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C024913:LivK protein, E coli; D033902:Periplasmic Binding Proteins; D000604:Amino Acyl-tRNA Synthetases; D007935:Leucine-tRNA Ligase; D007930:Leucine