Primacy structure of two cytolysin isoforms from Stichodactyla helianthus differing in their hemolytic activity.

Sticholysin I (St-I) and sticholysin II (St-II) are cytolysins purified fro m the yea anemone Stichodactyla helianthus with a high degree of sequence i dentity (93%) but clearly differenced in their hemolytic activity. In order to go further into the structural determinants for the different behavior of St-I and St-II, we report here the complete amino acid sequences and the consensus secondary structure prediction of both proteins. The complete de termination of St-II primary structure confirms the partial revision of cyt olysin III amino acid sequence. All nonconservative changes between St-I an d St-II are located at the N-terminal. According to our prediction these ch anges could be located at the same face of an a-helix during pore formation events and could account for the observed differences in hemolytic activit y between St-I and St-II. (C) 2001 Elsevier Science Ltd. All rights reserve d.