Identification of the haem-binding subunit of cytochrome b-245.
Cytochrome b-245 from neutrophil plasma membranes contains two types of subunit with apparent molecular masses from gel electrophoresis in the presence of SDS of 23 kDa and 76-92 kDa. Radiation-inactivation analysis revealed a single-exponential decay process for the visible absorption of the haem chromophore in the membrane, corresponding to a molecular mass of 21 +/- 5 kDa for the haem-containing polypeptide chain. Sedimentation equilibrium of the cytochrome solubilized by the detergent Triton N101 showed that the protein was polydisperse, with a molecular mass of approx. 350 kDa for the smallest detectable species. In another detergent, n-octyl beta-O-glucopyranoside (octyl glucoside), the molecular mass of the haem-containing particle was found to be 20-30 kDa. Thus the quaternary structure of the protein breaks down in this detergent. The haem group is inferred to be attached to the smaller subunit.
Nugent
J H
JH
Department of Biology, University College London, U.K.
Gratzer
W
W
Segal
A W
AW
D001665:Binding Sites; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002501:Centrifugation, Zonal; D003573:Cytochrome b Group / Q000097:blood* / Q000302:isolation & purification; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008291:Malate Dehydrogenase / Q000378:metabolism; D009504:Neutrophils
D003573:Cytochrome b Group; D046911:Macromolecular Substances; C035130:cytochrome b245; D006418:Heme; D008291:Malate Dehydrogenase