Son of Sevenless

Son of Sevenless (SOS)

Diagram of signal transduction pathways, including the role of SOS.

Son of Sevenless (SOS) is a guanine nucleotide exchange factor (GEF) that plays a critical role in the signal transduction pathways of eukaryotic cells. It is primarily involved in the activation of the Ras protein, which is a key player in the regulation of cell growth, differentiation, and survival.

Structure

SOS is a large, multi-domain protein that contains several functional regions. These include the pleckstrin homology domain, the Dbl homology domain, and the Ras exchange motif. The structure of SOS allows it to interact with various proteins and lipids within the cell, facilitating its role in signal transduction.

Function

The primary function of SOS is to activate Ras by facilitating the exchange of GDP for GTP on the Ras protein. This activation is a crucial step in the MAPK/ERK pathway, which is involved in transmitting signals from the cell surface to the nucleus, ultimately influencing gene expression and cellular responses.

Activation Mechanism

SOS is recruited to the plasma membrane by binding to the SH3 domain of the Grb2 adaptor protein, which is associated with activated receptor tyrosine kinases (RTKs). Once at the membrane, SOS interacts with Ras, promoting the release of GDP and the binding of GTP, thus activating Ras.

Role in Disease

Mutations or dysregulation of SOS can lead to aberrant activation of Ras, which is implicated in various cancers and developmental disorders. Understanding the precise mechanisms of SOS function and regulation is crucial for developing targeted therapies for these conditions.

Related Pages

• Ras protein family
• MAPK/ERK pathway
• Receptor tyrosine kinase
• Guanine nucleotide exchange factor