2Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, 142292 Pushchino, Moscow Region, Russia
* To whom correspondence should be addressed.
Received June 26, 2007; Revision received July 28, 2007
The influence of cultivation conditions of pseudotuberculosis bacteria on the spatial structure and the functional activity of nonspecific OmpF-like porin was studied by means of optical spectroscopy, scanning microcalorimetry, and bilayer lipid membrane technique. With this goal, porin samples isolated from microbial masses grown at different temperatures, nutrient medium densities, and growth phases were characterized. According to CD data, the porin samples under investigation represent beta-sheet proteins. It was found that the protein isolated from the colonial culture of pseudotuberculosis bacteria grown at low temperature has the most compact structure. Using intrinsic protein fluorescence, it was shown that different conditions of pseudotuberculosis bacteria cultivation (temperature, medium, growth phase) led to the changes in spectral properties of porin fluorescence due to the redistribution of the contributions of tyrosine and different classes of tryptophan residues to the total protein emission. Heat inactivation of porin samples was studied using CD spectroscopy, intrinsic protein fluorescence, and scanning microcalorimetry. Spatial features of the porin samples were found to affect their functional activities. Considering all these data, it is possible to correlate the spatial structure and functional activity of porin samples isolated under different cultivation conditions of bacteria and the composition of the outer membrane lipid matrix.
KEY WORDS: nonspecific OmpF-like porins, spatial structure, thermostability, functional activity, lipid matrix