G-protein

G-protein is a type of protein that plays a crucial role in cell signaling. It is named for its ability to bind to guanosine triphosphate (GTP) and guanosine diphosphate (GDP).

Function

G-proteins are involved in transmitting signals from a variety of stimuli outside a cell to its interior. These stimuli can include light, peptides, lipids, sugars, and proteins. The detailed mechanisms of their function vary widely, but in general, they are involved in a process known as signal transduction.

Structure

G-proteins are composed of three subunits: alpha (α), beta (β), and gamma (γ). The α subunit is the one that binds to GDP and GTP, and it is this binding and unbinding that allows the G-protein to function.

Types of G-proteins

There are several types of G-proteins, including G_s, G_i, and G_q. Each type has a different effect on the cell.

G_s protein

G_s proteins stimulate the production of cyclic AMP (cAMP), which acts as a second messenger in the cell.

G_i protein

G_i proteins inhibit the production of cAMP.

G_q protein

G_q proteins activate phospholipase C, which in turn produces two second messengers: inositol trisphosphate (IP3) and diacylglycerol (DAG).

Role in disease

Mutations in G-proteins can lead to a variety of diseases, including cancer, diabetes, and Albright's hereditary osteodystrophy.

See also

• Signal transduction
• Second messenger system
• G protein-coupled receptor

G-protein Resources
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