WHEAT ACETYL-COENZYME-A CARBOXYLASE - CDNA AND PROTEIN-STRUCTURE

cDNA fragments encoding part of wheat (Triticum aestivum) acetyl-CoA c arboxylase (ACC; EC 6.4.1.2) were cloned by PCR using primers based on the alignment of several biotin-dependent carboxylases. A set of over lapping clones encoding the entire wheat ACC was then isolated by usin g these fragments as probes. The cDNA sequence contains a 2257-amino a cid reading frame encoding a 251-kDa polypeptide. The amino acid seque nce of the most highly conserved domain, corresponding to the biotin c arboxylases of prokaryotes, is 52-55% identical to ACC of yeast, rat, and diatom. Identity with the available C-terminal amino acid sequence of maize ACC is 66%. The biotin attachment site has the typical eukar yotic EVMKM sequence. The cDNA does not encode an obvious chloroplast targeting sequence. Various cDNA fragments hybridize in Northern blots to a 7.9-kb mRNA. Southern analysis with cDNA probes revealed multipl e hybridizing fragments in hexaploid wheat DNA. Some of the wheat cDNA probes also hybridize with ACC-specific DNA from other plants, indica ting significant conservation among plant ACCs.