Identification of a small heat shock/α-crystallin protein in the scleractinian coral Madracis mirabilis (Duch. and Mitch.)

Immunological evidence is provided for the first time of a small heat shock/alpha-crystallin protein in the scleractinian coral Madracis mirabilis. The protein termed cp26, had a molecular weight of 26 000; it reacted with an antibody raised to a small heat shock/alpha-crystallin protein from Artemia franciscana and its production in corals was temperature sensitive. Corals collected from seawater at 25.5 degrees C or lower lacked cp26, but the protein was produced in some of these animals when they were heat shocked experimentally. When exposed naturally to high environmental temperatures for relatively short times, corals contained cp26 and responded to heat shock in the laboratory. Corals growing at elevated temperatures tended to die when subjected to additional heat stress. Specifically, M. mirabilis died at about 31-33 degrees C, as indicated by visual inspection of the animals, low recovery of protein in cell-free extracts, and loss of protein bands in SDS-polyacrylamide gels. Death was accompanied by the appearance of a diffuse, unidentified protein band on western blots that reacted with an antibody to cp26. Madracis mirabilis clearly reacts to heat shock by production of cp26; further study is required to determine if this small heat shock/alpha-crystallin protein will be a useful biomarker of stress in corals.