Analysis of protein complexes in the unicellular cyanobacterium Cyanothece ATCC 51142

ABSTRACT: The unicellular cyanobacterium Cyanothece ATCC 51142 is capable of oxygenic photosynthesis and biological N2-fixation (BNF), a process highly sensitive to oxygen. Previous work has focused on determining protein expression levels under different growth conditions. A major gap of our knowledge is an understanding how these expressed proteins are assembled into complexes and organized into metabolic pathways, an area that has not been thoroughly investigated. Here, we combined size-exclusion chromatography (SEC) with label-free quantitative mass spectrometry (MS) and bioinformatics to characterize many protein complexes in the soluble fraction from Cyanothece 51142 cells grown under 12-h light-dark cycle. We identified 1386 proteins in duplicate biological replicates, and 64% of those proteins were identified as putative complexes. Pair-wise computational prediction of protein-protein interaction (PPI) identified 74,822 putative interactions, of which 2337 interactions were highly correlated with published protein co-expressions. Many sequential glycolytic and TCA cycle enzymes were identified as putative complexes. We also identified many membrane complexes that contain cytoplasmic domains. Subunits of NDH-1 complex eluted in a fraction with an approximate mass of ~669 kDa, and subunits composition revealed co-existence of distinct forms of NDH-1 complex subunits responsible for respiration, electron flow and CO2 uptake. The complex form of the phycocyanin beta subunit was non-phosphorylated and the monomer form was phosphorylated at Ser20, suggesting phosphorylation-dependent de-oligomerization of the phycocyanin beta subunit. This study provides an analytical platform for future studies to reveal how these complexes assemble and disassemble as a function of diurnal and circadian rhythms.

INSTRUMENT(S): Q Exactive Orbitrap HF

ORGANISM(S): Cyanothece Sp. Atcc 51142 (ncbitaxon:43989)

SUBMITTER: Uma K Aryal  

PROVIDER: MSV000082916 | MassIVE |

REPOSITORIES: MassIVE