This family of short proteins includes DNA-damage-inducible protein I (DinI) and related proteins. The SOS response, a set of cellular phenomena exhibited by eubacteria, is initiated by various causes that include DNA damage-induced replication arrest, and is positively regulated by the co- protease activity of RecA. Escherichia coli DinI, a LexA-regulated SOS gene product, shuts off the initiation of the SOS response when overexpressed in vivo. Biochemical and genetic studies indicated that DinI physically interacts with RecA to inhibit its co-protease activity [1]. The structure of DinI is known [2].

1: An NMR study on the interaction of Escherichia coli DinI with RecA-ssDNA complexes. Yoshimasu M, Aihara H, Ito Y, Rajesh S, Ishibe S, Mikawa T, Yokoyama S, Shibata T; Nucleic Acids Res 2003;31:1735-1743. PMID:12626715

2: Solution structure of DinI provides insight into its mode of RecA inactivation. Ramirez BE, Voloshin ON, Camerini-Otero RD, Bax A; Protein Sci 2000;9:2161-2169. PMID:11152126