New Type of Subchloroplast Fragments Isolated from Pea Chloroplasts by Digitonin
Heavy fragments have been isolated from pea chloroplasts by digitonine treatment and differential centrifugation.. The chlorophyll <i>a/b </i>ratio, proteins of photosystem I and ATPase have been essentially reduced in these particles as well as amount of P700. The content of photosystem II proteins decreased insignificantly, and amount of proteins of light-harvesting complex II did not change. Changes specifying reduction in content of photosystem I have been revealed in absorption spectra as well as in low temperature fluorescence spectra. Using electron microscopy images of ultra-thin sections of the heavy fragment preparations they have been shown to be chloroplast grana with reduced amount of thylakoids. But a thylakoid diameter was practically the same as in chloroplasts. Comparison of various characteristics of the fragments and chloroplasts from which the fragments have been isolated, revealed a high extent of integrity in margin areas in thylakoids of the fragments. An analysis of the obtained results shows, that developed procedure of fragmentation allows to obtain grana of a high extent of thylakoid integrity. The phenomenon of reduction in thylakoid amount per grana in our heavy fragments is considered on a basis of earlier proposed hypothesis concerning features of grana organization in its transversal direction.