The presence of glutamine synthetase in the thylakoids of nitrogen‐fixing cyanobacterium Nostoc muscorum

Abstract

The intracellular distribution of glutamine synthetase (GS) in cell-free extracts of Nostoc muscorum has been investigated. 64-73% of the enzyme activity was associated with the thylakoid membranes. No enzyme activity was found in cytoplasmic membranes. 92% inhibition of the enzyme activity was obtained with an antiserum raised to the thylakoids using Triton-treated membranes, in comparison to 7.95% inhibition with the intact membranes. This suggests that the majority of the enzyme is embedded inside these membranes. This was also supported by the effect of pronase on the exposed glutamine synthetase using intact membranes.