Table of Contents
International Journal of Evolutionary Biology
Volume 2009 (2009), Article ID 715086, 10 pages
http://dx.doi.org/10.4061/2009/715086
Research Article

Divergence of AMP Deaminase in the Ice Worm Mesenchytraeus solifugus (Annelida, Clitellata, Enchytraeidae)

1Department of Biology, University of Milano, via Celoria 26, 20133 Milano, Italy
2Department of Biology, Rutgers The State University of New Jersey, 315 Penn Street, Science Building, Camden, NJ 08102, USA

Received 7 April 2009; Accepted 22 May 2009

Academic Editor: Dan Graur

Copyright © 2009 Roberto Marotta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Glacier ice worms, Mesenchytraeus solifugus and related species, are the largest glacially obligate metazoans. As one component of cold temperature adaptation, ice worms maintain atypically high energy levels in an apparent mechanism to offset cold temperature-induced lethargy and death. To explore this observation at a mechanistic level, we considered the putative contribution of adenosine monophosphate deaminase (AMPD), a key regulator of energy metabolism in eukaryotes. We cloned cDNAs encoding ice worm AMPD, generating a fragment encoding 543 amino acids that included a short N-terminal region and complete C-terminal catalytic domain. The predicted ice worm AMPD amino acid sequence displayed conservation with homologues from other mesophilic eukaryotes with notable exceptions. In particular, an ice worm-specific K188E substitution proximal to the AMP binding site likely alters the architecture of the active site and negatively affects the enzyme's activity. Paradoxically, this would contribute to elevated intracellular ATP levels, which appears to be a signature of cold adapted taxa.