Stealth_CR2 is the second of several highly conserved regions on stealth proteins in metazoa and bacteria. There are up to four CR regions on all member proteins. CR2 carries a well-conserved NDD sequence-motif. The domain is found in tandem with CR1, CR3 and CR4 on both potential metazoan hosts and pathogenic eubacterial species that are capsular polysaccharide phosphotransferases. The CR domains 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