The Vesicle-inducing Protein 1 from Synechocystis sp. PCC 6803 Organizes into Diverse Higher-Ordered Ring Structures

Abstract

The vesicle-inducing protein in plastids 1 (Vipp1) was found to be involved in thylakoid membrane formation in chloroplasts and cyanobacteria. In contrast to chloroplasts, it has been suggested that in cyanobacteria the protein is only tightly associated with the cytoplasmic membrane. In the present study we analyze and describe the subcellular localization and the oligomeric organization of Vipp1 from the cyanobacterium Synechocystis PCC 6803. Vipp1 forms stable dimers and higher-ordered oligomers in the cytoplasm as well as at both the cytoplasmic and thylakoid membrane. Vipp1 oligomers are organized in ring structures with a variable diameter of 25-33 nm and corresponding calculated molecular masses of approximately 1.6-2.2 MDa. Six different types of rings were found with an unusual 12-17-fold symmetrical conformation. The simultaneous existence of multiple types of rings is very unusual and suggests a special function of Vipp1. Involvement of diverse ring structures in vesicle formation is suggested.