The 70‐kDa major DNA‐compacting protein of the chloroplast nucleoid is sulfite reductase

Abstract

The chloroplast nucleoid is a complex of chloroplast DNA and various, mostly uncharacterized proteins. An abundant 70-kDa protein of the isolated nucleoids of pea chloroplasts was identified as sulfite reductase by N-terminal sequence analysis as well as immunoblot analysis, spectrophotometry and enzyme activity analysis. Recombinant maize sulfite reductase was indeed able to compact chloroplast DNA and to form nucleoid-like particles in vitro. The role of sulfite reductase in the structural organization of the nucleoid is discussed.