THE PUTATIVE ACETYL-COA SYNTHETASE GENE OF CRYPTOSPORIDIUM-PARVUM ANDA NEW CONSERVED PROTEIN MOTIF IN ACETYL-COA SYNTHETASES

We determined the nucleotide (nt) sequence of the putative gene encodi ng acetyl-coenzyme A synthetase (ACS) from the parasitic protozoan Cry ptosporidium parvum. The gene is single copy, located on a chromosome of approximately 1.08 mb, and has no introns. The gene is characterize d by low codon usage bias and encodes a 694-amino acid (aa) protein wi th a predicted molecular size of 78 kDa, similar to other ACSs from di fferent prokaryotic and eukaryotic species. Comparison of multiple pro tein alignments of ACSs revealed a new conserved sequence motif PKT(R/ V/L)SGK(I/V/T)(T/M/V/K)R(R/N) near the C-terminus, which may be a sign ature for ACSs. This motif shares significant homology with sequences from other members of the AMP-binding family, has secondary structure similar to the purine-bindmg motif of ATP- and GTP-ases, and may play a role in the enzymatic activity of proteins from the AMP-binding fami ly.