Glutathione-S-transferases have been identified in all the living species examined so far, yet little is known about their function in marine organisms. In a previous report, the recently identified GST from Antarctic bivalve Laternula elliptica (LeGST) was classified into the rho class GST, but there are several unique features of LeGST that may justify reclassification, which could represent specific shellfish GSTs. Here, we determined the crystal structure of LeGST, which is a shellfish specific class of GST. The structural analysis showed that the relatively open and wide hydrophobic H-site of the LeGST allows this GST to accommodate various substrates. These results suggest that the H-site of LeGST may be the result of adaptation to their environments as sedentary organisms. Proteins 2013. © 2012 Wiley Periodicals, Inc.