The YER057c/YIL051c/YjgF protein family is a set of 24 full-length homologs,
each approximately 130 residues in length, and each with no known function or
relationship to proteins of known structure. To determine the function of this
family, the structure of one member--the YjgF protein from Escherichia coli--was
solved and refined at a resolution of 1.2 A. The YjgF molecule is a homotrimer
with exact threefold symmetry. Its tertiary and quaternary structures are
related to that of Bacillus subtilis chorismate mutase, although their active
sites are completely different. The YjgF protein has an active site curiously
similar to protein tyrosine phosphatases, including a covalently modified
cysteine, but it is unlikely to be functionally related. The lessons learned
from this attempt to deduce function from structure may be useful to future
projects in structural genomics.
