Spatial mapping of a cyanobacterial proteome reveals distinct subcellular compartment organisation and dynamic metabolic pathways

Cyanobacteria are complex prokaryotes, incorporating a Gram-negative cell wall and internal thylakoid membranes. However, localisation of proteins within cyanobacterial cells is poorly understood. Using subcellular fractionation and quantitative proteomics we report the most extensive subcellular map of the proteome of a cyanobacterial cell, identifying ~67% of Synechocystis sp. PCC 6803 proteins, ~1000 more than previous studies. 1,712 proteins were assigned to six specific subcellular regions. Proteins involved in energy generation localised to thylakoid membranes whereas transporters and regulatory proteins predominantly reside in the plasma membrane. The majority of metabolic enzymes are soluble although numerous biosynthetic pathways terminate in membranes. Ribosomal proteins and enzymes synthesising the storage compound polyhydroxybuyrate localise to distinct regions of the cell. Moreover, heterogeneity within membrane and cytoplasmic regions is observed, indicating further cellular complexity. Cyanobacteria thylakoid membrane protein localisation is conserved in Arabidopsis thaliana chloroplasts, suggesting similar proteome organisation in higher photosynthetic organisms. The dynamic organisation of a cyanobacterial cell we reveal will aid our understanding of these environmentally and biotechnological important organisms.

Laura L. Baers¹, Lauren A. Mills², Laurent. Gatto¹, Lisa M. Breckels¹, Michael J. Deery¹, Tim J. Stevens³, Christopher J. Howe¹, Kathryn S. Lilley^1,4, David J. Lea-Smith².

¹ Department of Biochemistry, Hopkins Building, Downing Site, University of Cambridge, CB2 1QW, United Kingdom

² School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK

³ MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom

⁴ Cambridge Systems Biology Centre, and Cambridge Centre for Proteomics

More information on Dr David Lea-Smith.