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Identification of individual amino acids required for secretion within the haemolysin (HlyA) C ‐terminal targeting region
Author(s) -
Kenny Brendan,
Taylor Sally,
Holland I. Barry
Publication year - 1992
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.1365-2958.1992.tb00868.x
Subject(s) - secretion , biology , hemolysin , escherichia coli , bacterial outer membrane , biochemistry , signal peptide , microbiology and biotechnology , peptide sequence , gene , virulence
Summary The release of haemolysin from Escherichia coli involves direct secretion across both the inner and outer membranes. Secretion of HlyA is dependent upon a specific membrane export complex composed of HlyB, ‐D and possibly TolC. HlyA is targeted to the medium via the membrane translocation complex, by a novel C ‐terminal secretion signal. Previous studies involving deletion and fusion analyses have given contradictory results for the minimal length (20–60 residues) of this HlyA signal region and little is known of the nature of the specific residues and structural features required for function. In this study we have analysed, quantitatively, the effect upon secretion of many point mutations introduced into the HlyA C ‐terminus. The results indicate the presence of a minimal secretion signal domain whose proximal boundary extends to at least residue –46 and which contains at least four Individual residues essential for maximal secretion levels. We propose that such residues act co‐operatively, forming multiple contact points with the translocator proteins, with the ‘best fit’ promoting maximal levels of secretion.