Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The NADPH oxidase of phagocytic cells is important for the efficient killing and digestion of ingested microbes. A very unusual low-potential cytochrome b (b-245) is the only redox molecule to have been identified in this system. The FAD-containing flavoprotein that binds NADPH and transfers electrons to the cytochrome has eluded identification for three decades. We show here that the haem/FAD ratio in the membranes does not change significantly on activation of this oxidase, indicating that the FAD is present in the membranes from the outset and not recruited from the cytosol. The FAD content of membranes from cells of patients with X-linked chronic granulomatous disease (CGD) lacking the cytochrome b was roughly one-quarter of that in normal subjects and in autosomal recessive CGD patients lacking the cytosolic protein p47-phox. Similar low amounts of FAD were present in uninduced promyelocytic (HL60) cells, suggesting that the low amount of FAD in cells from X-CGD patients was probably unrelated to this oxidase system. Cytochrome b-245 appears to bind both the haem and FAD, in a molar ratio of 2:1. The e.p.r. signal of the purified cytochrome was weak and had an asymmetric g(z) peak at g = 3.31. The purified cytochrome could be partially reflavinated (about 20%) in the presence of lipid. Amino acid sequence homology was detected between the beta-subunit of this cytochrome b and the ferredoxin-NADP+ reductase (FNR) family of reductases in the putative NADPH- and FAD-binding sites. 32P-labelled 2-azido-NADP was used as a photoaffinity label for the NADPH-binding site. Labelling that was competed off with NADP was observed in the region of the beta-subunit of the cytochrome. No labelling was seen in this region in X-CGD in three subjects in whom this cytochrome was missing and in a third in whom it was present but bore a Pro-His transposition in the putative NADPH-binding site. These studies indicate that cytochrome b-245 is a flavocytochrome, the first described in higher eukaryotic cells, bearing the complete electron-transporting apparatus of the NADPH oxidase.
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PMID:Cytochrome b-245 is a flavocytochrome containing FAD and the NADPH-binding site of the microbicidal oxidase of phagocytes. 132 Mar 78

Chronic granulomatous disease (CGD) is characterized by the failure of activated phagocytes to generate superoxide. Defects in at least four different genes lead to CGD. Patients with the X-linked form of CGD have mutations in the gene for the beta-subunit of cytochrome b558 (gp91-phox). Patients with a rare autosomal recessive form of CGD have mutations in the gene for the alpha-subunit of this cytochrome (p22-phox). Usually, this leads to the absence of cytochrome b558 in the phagocytes (A22(0) CGD). We studied the molecular defect in five European patients from three unrelated families with this type of CGD. P22-phox mRNA was reverse-transcribed, and the coding region was amplified by PCR in one fragment and sequenced. Three patients from one family, with parents that were first cousins, were homozygous for a single base substitution (G-297-->A) resulting in a nonconservative amino acid change (Arg-90-->Gln). This mutation was previously found in a compound heterozygote A22(0) CGD patient. Another patient, also from first-cousin parents, was homozygous for an A-309-->G mutation in the open reading frame that predicts a nonconservative amino acid replacement (His-94-->Arg). The fifth patient was also born from a first-cousin marriage and was shown to be homozygous for the absence of exon 4 from the cDNA. In this patient, a G-->A substitution was found at position 1 of intron 4 in the genomic DNA. Therefore, the absence of exon 4 in the cDNA of this patient is due to a splicing error.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cytochrome b558-negative, autosomal recessive chronic granulomatous disease: two new mutations in the cytochrome b558 light chain of the NADPH oxidase (p22-phox). 141 54

Chronic granulomatous disease (CGD) is characterized by the absence of a respiratory burst in activated phagocytes. Defects in at least four different genes lead to CGD. Patients with the X-linked form of CGD have mutations in the gene for the beta-subunit of cytochrome b558 (gp91-phox). We studied the molecular defect in four patients with X-linked CGD. In a fifth family, we studied the mother of a patient with X-linked CGD who had died before our investigations. Gp91-phox messenger RNA (mRNA) was reverse transcribed into cDNA and the coding region was amplified by polymerase chain reaction into three fragments. Sequence analysis showed the absence of the exon 7, 5, 3, and 2 sequences in patients 1, 2, 3, and 4, respectively. In carrier 5, we found both normal cDNA and cDNA that lacked 57 3'-nucleotides of exon 6. We analyzed the splice sites of the flanking introns of the missing exons. In patients 1, 2, and 3, we found single nucleotide substitutions within the first five positions of the down-stream 5' donor splice sites. In patient 4, a similar substitution was found at position -1 of the 3' acceptor splice site of intron 1. In carrier 5, no mutation was found in the exon 6-intron 6 boundary sequence. Instead, a single substitution was observed in exon 6 (C----A at nucleotide 633) that created a new donor splice site. Apparently, mRNA splicing occurs preferentially at this newly created splice site. We conclude that the absence of the exon sequences in the gp91-phox mRNA of these patients is due to splicing errors. Of 30 European X-linked CGD patients studied by us so far, five appear to be caused by mutations that affect correct mRNA splicing. Thus, such mutations appear to be a common cause of X-linked CGD.
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PMID:Splice site mutations are a common cause of X-linked chronic granulomatous disease. 152 Aug 80

The NADPH:O2 oxidoreductase of phagocytic leukocytes is an important enzyme for the bactericidal activity of these cells. Cytochrome b558 is a membrane component of this enzyme. In X-linked chronic granulomatous disease (Xb- CGD) the phagocytes are defective in the beta-subunit (gp91-phox) of this cytochrome. We have studied the genetic defect in a group of six X-linked CGD patients characterized by complete or partial loss of cytochrome b558 with the use of the polymerase chain reaction. All patients had a different single point mutation in the gp91-phox gene, indicating that the genetic defect in Xb- CGD is very heterogeneous. In one patient the mutation leads to a premature termination codon. In the other five cases these mutations predict incorporation of a different amino acid. The mutations were with one exception found in the N-terminal half of the protein, suggesting that this part of cytochrome b558 is important for the binding of the heme or for formation of a stable complex with p22-phox. Two histidyl residues were found that might be ligands of the heme iron.
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PMID:Point mutations in the beta-subunit of cytochrome b558 leading to X-linked chronic granulomatous disease. 171 Jan 53

Two of the cytosolic NADPH oxidase components, p47-phox and p67-phox, translocate to the plasma membrane in normal neutrophils stimulated with phorbol myristate acetate (PMA). We have now studied the translocation process in neutrophils of patients with chronic granulomatous disease (CGD), an inherited syndrome in which the oxidase system fails to produce superoxide due to lesions affecting any one of its four known components: the gp91-phox and p22-phox subunits of cytochrome b558 (the membrane-bound terminal electron transporter of the oxidase), p47-phox, and p67-phox. In contrast to normal cells, neither p47-phox nor p67-phox translocated to the membrane in PMA-stimulated CGD neutrophils which lack cytochrome b558. In one patient with a rare X-linked form of CGD caused by a Pro----His substitution in gp91-phox, but whose neutrophils have normal levels of this mutant cytochrome b558, translocation was normal. In two patients with p47-phox deficiency, p67-phox failed to translocate, whereas p47-phox was detected in the particulate fraction of PMA-stimulated neutrophils from two patients deficient in p67-phox. Our data suggest that cytochrome b558 or a closely linked factor provides an essential membrane docking site for the cytosolic oxidase components and that it is p47-phox that mediates the assembly of these components on the membrane.
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PMID:Neutrophil nicotinamide adenine dinucleotide phosphate oxidase assembly. Translocation of p47-phox and p67-phox requires interaction between p47-phox and cytochrome b558. 198 7

The pathobiology of chronic granulomatous disease (CGD) of childhood, a heterogeneous phenotypic disorder characterized by chronic and recurrent infection, has become more completely understood over the past three decades. Blood neutrophils, monocytes, and eosinophils lack a respiratory burst required for effective killing of catalase positive bacteria by reduced by-products of oxygen. The disease is transmitted in at least two genetic forms: X-linked and autosomal recessive. In the X-linked form, a gene coding for a beta subunit protein required for cytochrome b presence on the plasma membrane of phagocytic cells is not expressed. The protein appears to be a constituent of the cytochrome b complex that requires an additional alpha subunit for complete expression. Cytochrome b is likely a component of leukocyte oxidase, which catalyzes the respiratory burst. The autosomal recessive form of the disorder appears to be controlled by a set of genes coding for soluble cofactors essential for oxidase expression. One or more of these cofactors have recently been shown to be deficient in several patients with autosomal recessive CGD. Optional therapy for CGD patients is presently not available. Long-term use of antibiotics may be helpful. The cloned product interferon gamma has been reported to improve superoxide generation, bactericidal activity, and immunoreactive cytochrome b in some CGD neutrophils and monocytes, both in vitro and in vivo. Currently a prospective clinical evaluation of the efficacy of interferon gamma is in progress. Molecular studies of expression and function of the X-CGD gene in phagocytic cells are in progress as well.
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PMID:Chronic granulomatous disease of childhood: clinical, pathological, biochemical, molecular, and genetic aspects of the disease. 210 36

We examined the potential of interferon gamma (IFN-gamma) to ameliorate the physiologic defect of chronic granulomatous disease (CGD) by studying its effects on CGD phagocyte superoxide generation, NADPH oxidase kinetics, cytochrome b559 content, and expression of X-CGD (the gene for the X-linked disease). Granulocytes and macrophages from three patients in two kindreds with "variant" X-linked CGD (i.e., with very low, but detectable, baseline superoxide-generating activity) responded to IFN-gamma with enhanced nitroblue tetrazolium reduction and two- to eightfold increases in superoxide generation. IFN-gamma did not augment the respiratory burst activity of phagocytes from patients with "classic" CGD (i.e., no detectable baseline superoxide generation) or autosomal variant CGD. Incubation of a responding patient's granulocytes with IFN-gamma nearly doubled the maximal velocity for the NADPH oxidase, but did not change its abnormal Michaelis constant. Although the interferon-treated CGD granulocytes produced superoxide at a rate 40% of normal, the cytochrome b spectrum remained undetectable. IFN-gamma treatment of cultured monocytes from an IFN-gamma-responsive CGD patient increased the steady state level of RNA transcripts from the X-CGD gene from barely detectable up to approximately 5% of normal.
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PMID:Recombinant interferon gamma augments phagocyte superoxide production and X-chronic granulomatous disease gene expression in X-linked variant chronic granulomatous disease. 282 Oct 69

Chronic granulomatous disease is an inherited disorder characterized by the failure of phagocytic cells to produce superoxide upon the ingestion of microorganisms due to a lesion in a membrane-associated NADPH-oxidase. The components of the oxidase have been incompletely characterized by standard biochemical approaches. A genetic strategy has recently led to the identification of the gene affected in the common X-linked form of CGD without reference to its protein product. The X-CGD gene, assigned to chromosome position Xp21.1, encodes a phagocyte-specific RNA transcript that is mutated in patients with X-CGD. Antisera directed toward the predicted protein product of the X-CGD gene recognize a 90 kD membrane glycoprotein, which corresponds to the larger subunit of the phagocyte b-cytochrome heterodimer. The recent genetic and biochemical findings provide an explanation for the consistent absence of the b-cytochrome spectrum in X-CGD, and establish this cytochrome as an essential component of the phagocyte oxidase. The primary amino acid sequence of both the 90 kD b-cytochrome subunit and the 22 kD subunit (cloned as the cDNA using a specific antisera) have no significant similarity to other proteins, including previously studied cytochromes. As both subunits of the b-cytochrome heterodimer are absent in X-CGD, despite a genetic deficiency of only the larger polypeptide, a close interaction between the two subunits may be important for b-cytochrome stability and function. Expression of the b-cytochrome large subunit mRNA is increased by interferon-gamma, an important macrophage activator. Partial or complete restoration of oxidase activity in some X-CGD patients treated with interferon-gamma suggests new therapeutic approaches in the management of this disorder. Molecular reagents prepared from the cloned X-CGD cDNA or gene may prove to be clinically useful in prenatal diagnosis and may provide a basis for somatic gene therapy in future.
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PMID:Molecular genetics of chronic granulomatous disease. 307 10

Chronic granulomatous disease is an inherited disorder of microbial killing characterized by the failure of phagocytic cells to produce superoxide due to a lesion in a membrane-associated NADPH-oxidase. The components of the oxidase have been incompletely characterized and, therefore, a genetic approach has been used to identify the gene affected in the common X-linked form of CGD without reference to a specific protein product. The X-CGD gene was first mapped to Xp21.1. A phagocyte-specific RNA transcript derived from Xp21 was identified and shown to be deficient (or disrupted) in patients with X-CGD. Antisera directed toward the predicted protein product of the X-CGD gene have established its identity as a 90-kD membrane glycoprotein and a component of the phagocyte cytochrome b, recently purified as a heterodimer of a 90-kD species and a 22-kD polypeptide. The more recent genetic and biochemical findings now provide an explanation for the consistent absence of the phagocyte cytochrome b spectrum in X-CGD (now termed "X- -CGD"). Both subunits of the cytochrome b heterodimer are absent in X- -CGD, despite a genetic deficiency of only the larger polypeptide, which indicates that a complete understanding of cytochrome biosynthesis and function will require further characterization of the small subunit. We should anticipate that identification of other functionally associated proteins will aid in analysis of the phagocyte oxidase. Molecular reagents prepared from the cloned X-CGD cDNA or gene may prove to be clinically useful in prenatal diagnosis and may provide a basis for somatic gene therapy in the future.
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PMID:Chronic granulomatous disease. Molecular genetics. 329 8

The clinical, biochemical, and molecular analysis of a patient with chronic granulomatous disease (CGD), retinitis pigmentosa (RP), and McLeod phenotype and of his parents demonstrated the X-linked transmission of these three traits in this family and a deletion of the entire X-CGD gene of the patient DNA. All but one other DNA markers tested, including those in Xp21, were present. These findings strongly suggest that the McLeod locus and at least one XL RP gene are closely linked to the X-CGD locus in the Xp21 region of the human X chromosome.
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PMID:Xp21 DNA microdeletion in a patient with chronic granulomatous disease, retinitis pigmentosa, and McLeod phenotype. 341 9


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