Members of this family are predominantly found in prokaryotic prolyl-tRNA synthetase. They contain a zinc binding site, and adopt a structure consisting of alpha helices and antiparallel beta sheets arranged in 2 layers, in a beta-alpha-beta-alpha-beta motif [1].

1: The structural basis of cysteine aminoacylation of tRNAPro by prolyl-tRNA synthetases. Kamtekar S, Kennedy WD, Wang J, Stathopoulos C, Soll D, Steitz TA; Proc Natl Acad Sci U S A. 2003;100:1673-1678. PMID:12578991