This is a family of transcriptional regulators. CaiF is involved in carnitine metabolism [1]. GrlA is encoded within the LEE type III secretion system in the enteropathogenic E. coli O157:H [2]. GrlR interacts with GrlA at its Helix-Turn-Helix (HTH) motif, preventing GrlA from binding to its target promoter DNA.

1: Identification and characterization of the caiF gene encoding a potential transcriptional activator of carnitine metabolism in Escherichia coli. Eichler K, Buchet A, Lemke R, Kleber HP, Mandrand-Berthelot MA; J Bacteriol. 1996;178:1248-1257. PMID:8631699

2: Structure of GrlR-GrlA complex that prevents GrlA activation of virulence genes. Padavannil A, Jobichen C, Mills E, Velazquez-Campoy A, Li M, Leung KY, Mok YK, Rosenshine I, Sivaraman J; Nat Commun. 2013;4:2546. PMID:24092262