We have used differential scanning calorimetry to study the effects of phalloidin on F and G actin stability. For F actin, saturating concentrations of phalloidin induced an important shift on the transition temperature, Tm, from 69.5 degrees C to 83.5 degrees C. However, the calorimetric enthalpy remained unchanged. Using lower phalloidin concentrations, monomers linked to phalloidin, as well as neighboring unlinked monomers, were both stabilized. Contrary to previous reports, phalloidin was also shown to affect G actin, shifting its Tm from 59.5 degrees C to 75 degrees C. Two mechanisms are proposed to explain this finding: first, it could indicate a real interaction of phalloidin with G actin, and second, heating of the specimen during the scan could have induced polymerization of some G actin to the F form. The resulting F polymer would then interact with phalloidin, thus shifting the equilibrium between G and F actin towards the polymeric form. Study holds ProTherm entries: 7165 Extra Details: phalloidin; calorimetric enthalpy; polymerization;,polymeric form
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:33 p.m.
|Number of data points||2|
|Proteins||Actin, alpha skeletal muscle ; Actin, alpha skeletal muscle|
|Assays/Quantities/Protocols||Experimental Assay: dHcal ; Experimental Assay: Tm|
|Libraries||Mutations for sequence A:DEDETTALVCDNGSGLVKAGFAGDDAPRAVFPSIVGRPRHQGVMVGMGQKDSYVGDEAQSKRGILTLKYPIEHGIITNWDDMEKIWHHTFYNELRVAPEEHPTLLTEAPLNPKANREKMTQIMFETFNVPAMYVAIQAVLSLYASGRTTGIVLDSGDGVTHNVPIYEGYALPHAIMRLDLAGRDLTDYLMKILTERGYSFVTTAEREIVRDIKEKLCYVALDFENEMATAASSSSLEKSYELPDGQVITIGNERFRCPETLFQPSFIGMESAGIHETTYNSIMKCDIDIRKDLYANNVMSGGTTMYPGIADRMQKEITALAPSTMKIKIIAPPERKYSVWIGGSILASLSTFQQMWITKQEYDEAGPSIVHR/D:LKIAAFNIRTFGETKMSNATLASYIVRIVRRYDIVLIQEVRDSHLVAVGKLLDYLNQDDPNTYHYVVSEPLGRNSYKERYLFLFRPNKVSVLDTYQYDDGCGNCGNDSFSREPAVVKFSSHSTKVKEFAIVALHSAPSDAVAEINSLYDVYLDVQQKWHLNDVMLMGDFNADCSYVTSSQWSSIRLRTSSTFQWLIPDSADTTATSTNCAYDRIVVAGSLLQSSVVPGSAAPFDFQAAYGLSNEMALAISDHYPVEVTLT|