title: Structural determinants of SecB recognition by SecA in bacterial protein translocation.
abstract: SecB is a bacterial chaperone involved in directing pre-protein to the translocation pathway by its specific interaction with the peripheral membrane ATPase SecA. The SecB-binding site on SecA is located at its C terminus and consists of a stretch of highly conserved residues. The crystal structure of SecB in complex with the C-terminal 27 amino acids of SecA from Haemophilus influenzae shows that the SecA peptide is structured as a CCCH zinc-binding motif. One SecB tetramer is bound by two SecA peptides, and the interface involves primarily salt bridges and hydrogen bonding interactions. The structure explains the importance of the zinc-binding motif and conserved residues at the C terminus of SecA in its high-affinity binding with SecB. It also suggests a model of SecB-SecA interaction and its implication for the mechanism of pre-protein transfer in bacterial protein translocation.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D015032:Zinc / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C057842:SecB protein, Bacteria; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins; D015032:Zinc