protein kinase C conserved region 1 (C1 domain) found in the kinase suppressor of Ras (KSR) family
KSR is a scaffold protein that functions downstream of Ras and upstream of Raf in the Extracellular signal-Regulated Kinase (ERK) pathway that regulates many cellular processes including cycle regulation, proliferation, differentiation, survival, and apoptosis. KSR proteins regulate the assembly and activation of the Raf/MEK/ERK module upon Ras activation at the membrane by direct association of its components. They are widely regarded as pseudokinases, but there is some debate in this designation as a few groups have reported detecting kinase catalytic activity for KSRs, specifically KSR1. Vertebrates contain two KSR proteins, KSR1 and KSR2. KSR proteins contain a SAM-like domain, a zinc finger cysteine-rich domain (C1), and a pseudokinase domain. This model describes the C1 domain. The C1 domain is a cysteine-rich zinc binding domain that does not bind DNA nor possess structural similarity to conventional zinc finger domains; it contains two separate Zn(2+)-binding sites.