Putative identification of an amphipathic alpha-helical sequence in hemolysin of Escherichia coli (HlyA) involved in transmembrane pore formation.
Abstract Escherichia coli hemolysin is a pore-forming protein belonging to the RTX toxin family. Cysteine scanning mutagenesis was performed to characterize the putative pore-forming domain of the molecule. A single cysteine residue was introduced at 48 positions within the sequence spanning residues 170-400 and labeled with the polarity-sensitive dye badan. Spectrofluorimetric analyses indicated that several amino acids in this domain are inserted into the lipid bilayer during pore formation. An amphipathic alpha-helix spanning residues 272-298 was identified that may line the aqueous pore. The importance of this sequence was highlighted by the introduction of two prolines at positions 284 and 287. Disruption of the helix structure did not affect binding properties, but totally abolished the hemolytic activity of the molecule.
Valeva
Angela
A
Institute of Medical Microbiology and Hygiene, University of Mainz, D-55101 Mainz, Germany. avaleva@uni-mainz.de
Siegel
Isabel
I
Wylenzek
Mark
M
Wassenaar
Trudy M
TM
Weis
Silvia
S
Heinz
Natalia
N
Schmitt
Robert
R
Fischer
Christina
C
Reinartz
Ricarda
R
Bhakdi
Sucharit
S
Walev
Iwan
I
D020816:Amino Acid Motifs; D000818:Animals; D045744:Cell Line, Tumor; D004910:Erythrocyte Membrane; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D018272:Porins / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011817:Rabbits
D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D050505:Mutant Proteins; D018272:Porins