E. coli YceI is a base-induced periplasmic protein [1]. The recent structure of a member of this family shows that it binds to poly-isoprenoid [2]. The structure consists of an extended, eight-stranded, antiparallel beta-barrel that resembles the lipocalin fold.

1: pH-Dependent Expression of Periplasmic Proteins and Amino Acid Catabolism in Escherichia coli. Stancik LM, Stancik DM, Schmidt B, Barnhart DM, Yoncheva YN, Slonczewski JL; J Bacteriol 2002;184:4246-4258. PMID:12107143

2: Crystal structure of a novel polyisoprenoid-binding protein from Thermus thermophilus HB8. Handa N, Terada T, Doi-Katayama Y, Hirota H, Tame JR, Park SY, Kuramitsu S, Shirouzu M, Yokoyama S; Protein Sci. 2005;14:1004-1010. PMID:15741337