This family includes the N-terminus of the actin-interacting protein sperm-specific antigen 2, or KRAP (Ki-ras-induced actin-interacting protein) [1]. This region is found to be the residues that interact with inositol 1,4,5-trisphosphate receptor (IP3R). KRAP was first localised as a membrane-bound form with extracellular regions suggesting it might be involved in the regulation of filamentous actin and signals from the outside of the cells [1]. It has now been shown to be critical for the proper subcellular localisation and function of IP3R. Inositol 1,4,5-trisphosphate receptor functions as the Ca2+ release channel on specialised endoplasmic reticulum membranes, so the subcellular localisation of IP3R is crucial for its proper function [2].

1: Deregulated expression of KRAP, a novel gene encoding actin-interacting protein, in human colon cancer cells. Inokuchi J, Komiya M, Baba I, Naito S, Sasazuki T, Shirasawa S; J Hum Genet. 2004;49:46-52. PMID:14673706

2: Determination of the critical region of KRAS-induced actin-interacting protein for the interaction with inositol 1,4,5-trisphosphate receptor. Fujimoto T, Machida T, Tsunoda T, Doi K, Ota T, Kuroki M, Shirasawa S; Biochem Biophys Res Commun. 2011;408:282-286. PMID:21501587