Molecular characterization in patients with chronic granulomatous disease due to p47phox deficiency

Abstract

NADPH oxidase system is an enzymatic electron transport complex localized in the membrane of phagocytic cells. Several proteins belong to this system: A flavocytochrome b558, formed by a b chain (gp91.phox) and an a chain (p22.phox) and, at least, 3 cytosolic proteins (p47.phox, p67.phox and p40 phox). Genetic alteration in any of these proteins causes the syndrome of Chronic Granulomatous Disease (CGD). Characterization of mutations in patients with CGD has been fundamental to elucidate the structure and function of NADPH oxidase system ComponentS. Several findings make p47.phoX an interesting model to study the molecular mechanism involved in regulating the expreSSion and bioChemical function ofthis system. So far, in patients with p47.phoX defect a deletion of dinucleotide GT has been foUnd at the beginning of exon 2; most of them are homocygotic for this deletion which is probably due to recombinant events between normal p47.phoX gen and a recently described pseudogen. Any mutation found when diagnosing non.homocygotic patients (gDNA or cDNA) may represent a pseudogen change. Therefore, for precise identification of the genetic defect it is necessary to separate the normal gen from the pseudogen and to analyze individual sequences. Non.homocygotic patients posibly have a second mutation in the wild type allele different fron GT deletion. On the other hand, through site. oriented mutagenesis it is posible to modify some of the aminoacids or domains of p47.phoX, which may be essential for its function and relationship with CGD. With this method010gy it is possible to introduce changes in a gen whoSe sequence is thoroughly known and which is amplified; mutants So generated can give information concerning the structure and function of the analyzed genes, observing their effect on function. In this way the importance of a structural change on the function of a protein can be determined.