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Conserved amino acids in the N‐ and C‐terminal domains of integral membrane transporter FhuB define sites important for intra‐ and intermolecular interactions
Author(s) -
Böhm Brigitte,
Boschert Hartmut,
Köster Wolfgang
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1996.tb02503.x
Subject(s) - periplasmic space , biology , integral membrane protein , biochemistry , membrane transport protein , amino acid , complementation , cytoplasm , conserved sequence , transmembrane domain , membrane transport , transporter , transport protein , membrane , peptide sequence , membrane protein , escherichia coli , transmembrane protein , function (biology) , biophysics , microbiology and biotechnology , mutant , gene , receptor
Summary Transport of iron(III) hydroxamates across the inner membrane of Escherichia coli is mediated by a periplasmic binding protein‐dependent transport (PBT) mechanism. FhuB, the integral membrane component of the system, is composed of covalently linked halves (FhuB[N] and FhuB[C]) which still function when present as two distinct polypeptide chains. Our analysis of two uptake‐deficient FhuB derivatives provides evidence for a mechanistically novel type of functional complementation:‘domain displacement’ in the cytoplasmic membrane. Amino acid residues 60 and 426 in the FhuB polypeptide chain may define key positions that are important for FhuB[N]–FhuB[C] interaction. Furthermore, FhuB derivatives, altered in either one of their conserved regions ‐ typical of PBT related integral membrane proteins ‐ displayed a dominant negative effect on ferric hydroxamate transport. The experimental data suggest that the two functionally equivalent conserved regions in FhuB[N] and FhuB[C] are primarily involved in the interaction with another component of the transport system, probably FhuC.