This domain is found in the N-terminal region of Chorismatase from (FkbO) and 3-hydroxybenzoate synthase (Hyg5) from Streptomyces hygroscopicus and in similar bacterial proteins. These enzymes catalyse the hydrolysis of chorismate into pyruvate and (dihydro)benzoic acid derivatives and are involved in the biosynthetic pathways forming polyketidic immunosuppressants such as ascomycin (FK520) and tacrolimus (FK506), which prevent T-cell proliferation through initial binding to the immunophilin FKBP12. FkbO is organised into three domains: N-terminal, central and C-terminal. This entry represents the N-terminal and central domains of FkbO, which show two beta-sheets and three alpha-helices. This fold is also found in Hyg5, which employ a fundamentally different reaction mechanism than the typical hydrolysis seen in FkbO [1-3].

1: Mechanistic implications for the chorismatase FkbO based on the crystal structure. Juneja P, Hubrich F, Diederichs K, Welte W, Andexer JN; J Mol Biol. 2014;426:105-115. PMID:24036425

2: Chorismatase Mechanisms Reveal Fundamentally Different Types of Reaction in a Single Conserved Protein Fold. Hubrich F, Juneja P, Muller M, Diederichs K, Welte W, Andexer JN; J Am Chem Soc. 2015;137:11032-11037. PMID:26247872

3: Biosynthesis of the immunosuppressants FK506, FK520, and rapamycin involves a previously undescribed family of enzymes acting on chorismate. Andexer JN, Kendrew SG, Nur-e-Alam M, Lazos O, Foster TA, Zimmermann AS, Warneck TD, Suthar D, Coates NJ, Koehn FE, Skotnicki JS, Carter GT, Gregory MA, Martin CJ, Moss SJ, Leadlay PF, Wilkinson B; Proc Natl Acad Sci U S A. 2011;108:4776-4781. PMID:21383123