This domain is found in the Major Vault Protein and has been called the shoulder domain [1]. This family includes two bacterial proteins Swiss:A6FXE2 and Swiss:A1ZGE7. This suggests that some bacteria may possess vault particles.

1: The structure of rat liver vault at 3.5 angstrom resolution. Tanaka H, Kato K, Yamashita E, Sumizawa T, Zhou Y, Yao M, Iwasaki K, Yoshimura M, Tsukihara T; Science. 2009;323:384-388. PMID:19150846