A NOVEL DYSTROPHIN UTROPHIN-ASSOCIATED PROTEIN IS AN ENZYMATICALLY INACTIVE MEMBER OF THE PHOSPHOGLUCOMUTASE SUPERFAMILY

A 60-kDa protein localised in adherens-type cellular junctions, and pr eviously called aciculin, has been found to interact with the cytoskel etal proteins dystrophin and utrophin [Belkin, A. M. & Burridge, K. (1 995) J. Biol. Chem. 270, 6328-6337]. In this study, we report the comp lete sequence of this protein, and show that it is a novel member of t he phosphoglucomutase (PGM) family of proteins. The PGM-related protei n (PGM-RP), which contains 506 amino acids (55.6 kDa), is smaller than PGM1 (566 amino acids, 61 kDa). The active site consensus sequences o f prokaryotic and eukaryotic mutases are not conserved in PGM-RP, a fi nding consistent with the lack of enzymatic activity of PGM-RP in vitr o, and the absence of a phosphorylated intermediate in vivo. The organ isation of the PGM-RP gene is essentially identical to that of PGM1. W e propose that the PGM-RP gene, which we have mapped to human chromoso me 9qcen-ql3, evolved from the PGM1 gene, and encodes a protein with a structural rather than an enzymatic role. PGM-RP is expressed predomi nantly in muscle with the highest levels in smooth muscle. The signifi cance of the interaction between dystrophin/utrophin and an increasing number of cytoplasmic proteins including PGM-RP remains to be explore d.