摘要Synechocystis sp.PCC 6803(hereafter:Synechocystis)is a model organism for studying photosynthesis,energy metabolism,and environmental stress.Although known as the first fully sequenced phototrophic organism,Synechocystis still has almost half of its proteome without func-tional annotations.In this study,by using co-fractionation coupled with liquid chromatography-tandem mass spectrometry(LC-MS/MS),we define 291 multi-protein complexes,encompassing 24,092 protein-protein interactions(PPIs)among 2062 distinct gene products.This information not only reveals the roles of photosynthesis in metabolism,cell motility,DNA repair,cell division,and other physiological processes,but also shows how protein functions vary from bacteria to higher plants due to changes in interaction partners.It also allows us to uncover the functions of hypothetical proteins,such as S110445,S110446,and S110447 involved in photosynthesis and cell motility,and Sill 334 involved in regulation of fatty acid biogenesis.Here we present the most exten-sive PPI data for Synechocystis so far,which provide critical insights into fundamental molecular mechanisms in cyanobacteria.