CYBB Gene

CYBB (CYBB stands for "cytochrome B-245 beta chain") is a protein-coding gene located on chromosome Xp21.1-p11. Associated signaling pathways include class I MHC-mediated antigen processing and presentation and G-protein signaling RAC1 in cellular processes.

Cytochrome b (-245) is composed of the alpha (CYBA) and beta (CYBB) chains. It functions as the major component of the phagocyte microbicidal oxidase system.

CYBB deficiency is one of the five described biochemical defects associated with chronic granulomatous disease (CGD). In this disease, phagocytic NADPH oxidase activity is decreased; neutrophils are able to phagocytose bacteria but cannot kill them in phagocytic vacuoles. The cause of the killing defect is the inability to increase cellular respiration and the consequent inability to deliver activated oxygen to the phagocytic vacuole.

Diseases associated with CYBB include:

• Immunodeficiency 34
• and
• Chronic granulomatous disease, X-linked (see alsoseptic granulomatosis).

The encoded protein is an important critical component of the membrane-bound oxidase of phagocytes , which generate superoxide. The protein is the final component of a respiratory chain that transfers single electrons from cytoplasmic NADPH across the plasma membrane to molecular oxygen on the outside. It also functions as a voltage-gated proton channel mediating the H(+) currents of resting phagocytes and is involved in the regulation of cellular pH. The protein is blocked by zinc.

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