Stealth_CR4 is the fourth highly conserved region on stealth proteins in metazoa and bacteria. There are four CR regions on mammalian members. CR4 carries a well-conserved CLND sequence-motif. The domain is found in tandem with CR1, CR2 and CR3 on both potential metazoan hosts and on pathogenic eubacterial species that are capsular polysaccharide phosphotransferases. The CR domains also appear on eukaryotic proteins such as GNPTAB, N-acetylglucosamine-1-phosphotransferase subunits alpha/beta. Horizontal gene-transfer seems to have occurred between host and bacteria of these sequence-regions in order for the bacteria to evade detection by the host innate immune system [1].

1: Stealth proteins: in silico identification of a novel protein family rendering bacterial pathogens invisible to host immune defense. Sperisen P, Schmid CD, Bucher P, Zilian O; PLoS Comput Biol. 2005;1:e63. PMID:16299590