Sticholysins I and II interaction with cationic micelles promotes toxins' conformational changes and enhanced hemolytic activity.
The effect of three cationic surfactants bearing the same polar head group and different chain length (cetyltrimethyl ammonium bromide (CTAB); tetradecyltrimethylammonium bromide (TTAB); dodecyltrimethylammonium bromide (DTAB)) on the conformation and function of the sea anemone pore-forming toxins sticholysins I and II (St I and St II) was studied by fluorescence and circular dichroism spectroscopy and evaluation of hemolytic activity (HA). Preincubation of the toxins with the longer chain surfactants CTAB and TTAB at concentrations slightly above their critical micelle concentration (CMC) leads to an enhancement of their HA. Significant increases in the fluorescence intensity with a slightly red shift in lambda(max) were observed at concentrations close to the surfactants' CMC, suggesting changes in the environment of the tryptophan residues. The changes in the fluorescence intensity are more noticeable and take place at lower surfactant concentrations for St I, irrespective of the surfactant alkyl chain length, although the differences between St I and St II increase as the surfactant alkyl chain length increases. This is evinced not only by the higher fluorescence intensity values and the lower surfactant concentrations required to reach them, but also by the higher acrylamide-quenching constant values (Ksv) for St I. However, the surfactant's effects on the toxins' HA were not found to be directly related to the observed changes in fluorescence intensity, as well as near- and far-UV-CD spectra. In particular, the latter spectra indicate that changes in HA and in fluorescence behavior take place without noticeable modifications in St I and St II secondary and tertiary structures. The results suggest that the interaction with the surfactants induces only subtle conformational changes in the toxins that favor the formation of lytic competent structures.
Center for Protein Studies, Faculty of Biology, University of Havana, Havana, Cuba.
María E
ME
Lanio
Carlos
C
Alvarez
Camila
C
Ochoa
Uris
U
Ros
Fabiola
F
Pazos
Diana
D
Martínez
Mayra
M
Tejuca
Luiz M
LM
Eugenio
Fábio
F
Casallanovo
Fabio H
FH
Dyszy
Shirley
S
Schreier
Eduardo
E
Lissi
D000818:Animals; D002412:Cations; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry; D002942:Circular Dichroism; D003064:Cnidarian Venoms / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D004912:Erythrocytes / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D008823:Micelles; D009930:Organic Chemicals / Q000737:chemistry / Q000494:pharmacology; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry / Q000494:pharmacology*; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000494:pharmacology*; D012615:Sea Anemones; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013501:Surface-Active Agents / Q000737:chemistry / Q000494:pharmacology*; D050337:Trimethyl Ammonium Compounds / Q000737:chemistry
D002412:Cations; D002593:Cetrimonium Compounds; D003064:Cnidarian Venoms; D004338:Drug Combinations; D008823:Micelles; D009930:Organic Chemicals; D052899:Pore Forming Cytotoxic Proteins; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D050337:Trimethyl Ammonium Compounds; C404794:sticholysin II; C121348:stycholysin I; C013912:decyltrimethylammonium; C009410:tetradecyltrimethylammonium; D000077286:Cetrimonium