Molecular Evolution of the AMP-forming Acetyl-CoA Synthetase. P. Capy 1, D. Karan 1,2, M. Lesbat 1. 1) Lab Population Genetics Evol, CNRS, Gif sur Yvette, France; 2) Department of Biochemistry and Molecular Biology, University of Nebraska, Medical Center, Omaha, USA.
AMP-forming Acetyl-CoA-Synthetase (ACS) is involved in the production of acetate, a major metabolite in numerous organisms. The gene is well conserved in all living species. Searches in databases showed 30 sequences related to the ACS. Most of these sequences were identified as ACS but three of them, belonging to the mammalian species, were annotated as another gene: SA, probably derived from a duplication of an ancestral gene. Six conserved regions of the ACS protein were defined. Among eukaryotes, we found a high variability with respect to the number and the position of introns. However, some positions are conserved between fungi and a nematode. A phylogenetic tree showed that all sequences belong to two groups: one the SA-like group and second, the ACS group. The later can be further divided in two parts: a prokaryotic one including eubacteria and an archaebacterium, and a eukaryotic group within which two proteobacterial sequences branch including ACS from the proteobacterium Rhodobacter capsulatus. Within the eukaryotic group, the data are consistent with the view that eukaryotes acquired their ACS gene from the ancestors of mitochondria. In Drosophilidae, analysis was done in 12 species. Four introns were detected. None of these introns shows a position similar to those known in the other species. The average length of intron varies from 65 to 75 bp but in two species D. takahashii and D. kikkawai the respective lengths of the second introns are 343 and 210 bp. Lengths of introns 1 and 3 are less variable than the other ones. Most of the introns cannot be aligned for the 12 species, except the introns 1 and 3 in the melanogaster subgroup suggesting that they are more constraint or more recent. In coding regions about 80%; of the 3rd codon positions are substituted and only 14%; and 6%; for the 1st and 2nd position respectively.