The J-binding protein 1 (JBP1) is essential for biosynthesis and maintenance of DNA base-J (beta-d-glucosyl-hydroxymethyluracil). Base-J and JBP1 are confined to some pathogenic protozoa and are absent from higher eukaryotes, prokaryotes and viruses. JBP1 recognizes J-containing DNA (J-DNA) through the DNA-Binding JBP1 domain (DB-JBP1), which binds to J-DNA with approximately the same affinity and specificity as full-length JBP1. Structure analysis of DB-JBP1 revealed a helix-turn-helix variant fold, a 'helical bouquet' with a 'ribbon' helix encompassing the amino acids responsible for DNA binding. Mutation of a single residue (Asp525) in the ribbon helix abrogates specificity toward J-DNA [1].

1: The structural basis for recognition of base J containing DNA by a novel DNA binding domain in JBP1. Heidebrecht T, Christodoulou E, Chalmers MJ, Jan S, Ter Riet B, Grover RK, Joosten RP, Littler D, van Luenen H, Griffin PR, Wentworth P Jr, Borst P, Perrakis A; Nucleic Acids Res. 2011;39:5715-5728. PMID:21415010