A missense mutation in the neutrophil cytochrome b heavy chain in cytochrome-positive X-linked chronic granulomatous disease.
A membrane-bound cytochrome b, a heterodimer formed by a 91-kD glycoprotein and a 22-kD polypeptide, is a critical component of the phagocyte NADPH-oxidase responsible for the generation of superoxide anion. Mutations in the gene for the 91-kD chain of this cytochrome result in the X-linked form of chronic granulomatous disease (CGD), in which phagocytes are unable to produce superoxide. Typically, there is a marked deficiency of the 91-kD subunit and the cytochrome spectrum is absent (X- CGD). In a variant form of CGD with X-linked inheritance, affected males have a normal visible absorbance spectrum of cytochrome b, yet fail to generate superoxide (X+ CGD). The size and abundance of the mRNA for the 91-kD subunit and its encoded protein were examined and appeared normal. To search for a putative mutation in the coding sequence of the 91-kD subunit gene, the corresponding RNA from an affected X+ male was amplified by the polymerase chain reaction and sequenced. A single nucleotide change, a C----A transversion, was identified that predicts a nonconservative Pro----His substitution at residue 415 of the encoded protein. Hybridization of amplified genomic DNA with allele-specific oligonucleotide probes demonstrated the mutation to be specific to affected X+ males and the carrier state. These results strengthen the concept that all X-linked CGD relates to mutations affecting the expression or structure of the 91-kD cytochrome b subunit. The mechanism by which the Pro 415----His mutation renders the oxidase nonfunctional is unknown, but may involve an impaired interaction with other components of the oxidase.
Dinauer
M C
MC
Division of Hematology Oncology, Children's Hospital Boston, Massachusetts 02115.
Curnutte
J T
JT
Rosen
H
H
Orkin
S H
SH
D001483:Base Sequence; D003573:Cytochrome b Group / Q000235:genetics*; D006105:Granulomatous Disease, Chronic / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009504:Neutrophils / Q000032:analysis*; D010586:Phagocytes / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D013481:Superoxides / Q000378:metabolism; D014960:X Chromosome
D003573:Cytochrome b Group; D012333:RNA, Messenger; D013481:Superoxides