of Suez while latrunculin B only exist in sponges in the gulf of Eilat. Why this is the case is still under investigation. Structure There are several isomers of latrunculin, A, B, C, D, G, H, M, S and T. The most common structures are latrunculin A and B. Their formulas are respectively C22H31NO5S and C20H29NO5S. The macrolactone ring on top that contains double bonds is a structural feature of the latrunculin molecules. The side chain contains an acylthiazolidinone substitute. Besides these natural occurring forms, scientist have made synthetic forms with different toxic strengths. Figure 2 shows some of these forms with their relative ability to disrupt microfilament activity. Semisynthetic forms that contained N-alkylated derivates were inactive. Mechanism of action Latrunculin A and latrunculin B affect polymerization of actin. Latrunculin binds actin monomers near the nucleotide binding cleft with 1:1 stoichiometry and prevents them from polymerizing. The nucleotide monomers are prevented from dissociation from the nucleotide binding cleft, thus preventing polymerizing. Experimental evidence shows that latruculin-A is biologically active in the solvent DMSO, but not in aqueous solutions, as demonstrated in cell culture and in brain tissue probably due to cellular permeation. When actin is impaired due to latrunculin, Shiga toxins have a better chance of infiltrating the intestinal epithelial monolayer in E. coli, which may cause a higher chance of generating gastrointestinal illnesses. It seems that actin monomers are more sensitive to bind latrunculin A than to bind Latrunculin B. In other words, latrunculin A is a more potent toxin. Latrunculin B is inactivated faster than latrunculin A. The prevention of polymerizing of the actin filaments causes reversible changes in the morphology of mammalian cells. Lantranculin interferes with the structure of the cytoskeleton in rats. After latrunculin B exposure, mouse fibroblasts grow bigger and PtK2 kidney cells from a potoroo stem produced long, branched extensions. The extensions seem to be an accumulation of actin monomers. Metabolism Yeast cells in absence of the proteins osh3 or osh5 demonstrated hypersensitivity to latrunculin B. The osh proteins are homologous to OSBP generated enzymes that appear in mammals, indicating that these might play a role in the toxicokinetics of latrunculins. Yeast mutants that are resistant to latrunculin show a mutation, D157E, that initiates a hydrogen bond with latrunculin. Other yeast mutants adjust the binding site, thus making it resistant to latrunculin. No research has been done to figure out how the biotransformation of