Open AccessLocalization of Vitamin B12 Binding in Euglena Gracilis
Author(s) -
Mario Houde,
Fathey Sarhan
Publication year - 1990
Publication title -
journal of general microbiology/journal of general microbiology
Language(s) - English
Resource type - Journals
eISSN - 2059-9323
pISSN - 0022-1287
DOI - 10.1099/00221287-136-3-529
Subject(s) - euglena gracilis , euglena , fractionation , vitamin b12 , cell , lysis , cuticle (hair) , binding site , biochemistry , vitamin , chemistry , fraction (chemistry) , cytolysis , cell fractionation , biology , biophysics , anatomy , chromatography , in vitro , enzyme , chloroplast , cytotoxic t cell , gene
Different fractionation procedures were used to determine the location of vitamin B12 binding sites in Euglena gracilis. Using uptake measurements, cell fractionation, and light and electron microscopy, the cuticle of the cell was found to be the fraction containing the majority of B12 binding sites. The apparent distribution of vitamin binding sites differed according to the cell lysis method used. The cuticle fraction was responsible for the binding of 80% of the vitamin taken up by the cell during both the rapid and the slow phase of uptake. These results suggest that vitamin B12 binding is regulated, in part, at the cuticle level, and support our previous conclusion that the secondary phase of uptake represents the synthesis of new receptor sites and not the unloading of vitamin inside the cell.