Inactivation of colicin Y by intramembrane helix-helix interaction with its immunity protein.
The construction of hybrids between colicins U and Y and the mutagenesis of the colicin Y gene (cya) have revealed amino acid residues important for interactions between colicin Y and its cognate immunity protein (Cyi). Four such residues (I578, T582, Y586 and V590) were found in helices 8 and 9 of the colicin Y pore-forming domain. To verify the importance of these residues, the corresponding amino acids in the colicin B protein were mutated to the residues present in colicin Y. An Escherichia coli strain with cloned colicin Y immunity gene (cyi) inactivated this mutant, but not the wild-type colicin B. In addition, interacting amino acid pairs in Cya and Cyi were identified using a set of Cyi point mutant strains. These data are consistent with antiparallel helix-helix interactions between Cyi helix T3 and Cya helix 8 of the pore-forming domain as a molecular mechanism of colicin Y inactivation by its immunity protein.
Smajs
David
D
Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic. dsmajs@med.muni.cz
Dolezalová
Magda
M
Macek
Pavel
P
Zídek
Lukás
L
D001665:Binding Sites; D003087:Colicins / Q000737:chemistry* / Q000378:metabolism; D048168:Escherichia coli K12 / Q000737:chemistry* / Q000276:immunology; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D007109:Immunity; D011485:Protein Binding; D017433:Protein Structure, Secondary
D003087:Colicins; C533450:Cyi protein, E coli; D029968:Escherichia coli Proteins; C533451:colicin Y protein, E coli