Heme transfer from streptococcal cell surface protein Shp to HtsA of transporter HtsABC.
Human pathogen group A streptococcus (GAS) can take up heme from host heme-containing proteins as a source of iron. Little is known about the heme acquisition mechanism in GAS. We recently identified a streptococcal cell surface protein (designated Shp) and the lipoprotein component (designated HtsA) of an ATP-binding cassette (ABC) transporter made by GAS as heme-binding proteins. In an effort to delineate the molecular mechanism involved in heme acquisition by GAS, heme-free Shp (apo-Shp) and HtsA (apo-HtsA) were used to investigate heme transfer from heme-containing proteins (holo proteins) to the apo proteins. In addition, the interaction between holo-Shp and holo-HtsA was examined using native polyacrylamide gel electrophoresis. Heme was efficiently transferred from holo-Shp to apo-HtsA but not from holo-HtsA to apo-Shp. Apo-Shp acquired heme from human hemoglobin, and holo-Shp and holo-HtsA were able to form a complex, suggesting that Shp actively relays heme from hemoglobin to apo-HtsA. These findings demonstrate for the first time complex formation and directional heme transfer between a cell surface heme-binding protein and the lipoprotein of a heme-specific ABC transporter in gram-positive bacteria.
Liu
Mengyao
M
Veterinary Molecular Biology, Montana State University, P.O. Box 173610, Bozeman, MT 59717, USA.
Lei
Benfang
B
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D013053:Spectrophotometry; D013297:Streptococcus pyogenes / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
D018528:ATP-Binding Cassette Transporters; D008565:Membrane Proteins; D006418:Heme