Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component

Authors

Fei Cai, University of California, BerkeleyFollow
Zhicheng Dou, University of Southern MississippiFollow
Susan L. Bernstein, University of California, BerkeleyFollow
Ryan Leverenz, rlleverenz@lbl.govFollow
Eric B. Williams, University of Southern MississippiFollow
Sabine Heinhorst, University of Southern MississippiFollow
Jessup M. Shively, Clemson UniversityFollow
Gordon C. Cannon, University of Southern MississippiFollow
Cheryl A. Kerfeld, University of California - Berkeley

Document Type

Article

Publication Date

6-2015

Department

Chemistry and Biochemistry

School

Mathematics and Natural Sciences

Abstract

The marine Synechococcus and Prochlorococcus are the numerically dominant cyanobacteria in the ocean and important in global carbon fixation. They have evolved a CO₂-concentrating-mechanism, of which the central component is the carboxysome, a self-assembling proteinaceous organelle. Two types of carboxysome, α and β, encapsulating form IA and form IB d-ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively, differ in gene organization and associated proteins. In contrast to the β-carboxysome, the assembly process of the α-carboxysome is enigmatic. Moreover, an absolutely conserved α-carboxysome protein, CsoS2, is of unknown function and has proven recalcitrant to crystallization. Here, we present studies on the CsoS2 protein in three model organisms and show that CsoS2 is vital for α-carboxysome biogenesis. The primary structure of CsoS2 appears tripartite, composed of an N-terminal, middle (M)-, and C-terminal region. Repetitive motifs can be identified in the N- and M-regions. Multiple lines of evidence suggest CsoS2 is highly flexible, possibly an intrinsically disordered protein. Based on our results from bioinformatic, biophysical, genetic and biochemical approaches, including peptide array scanning for protein-protein interactions, we propose a model for CsoS2 function and its spatial location in the α-carboxysome. Analogies between the pathway for β-carboxysome biogenesis and our model for α-carboxysome assembly are discussed.

Comments

Published by Life at 10.3390/life5021141.

Publication Title

Life

Volume

5

Issue

2

First Page

1141

Last Page

1171

Recommended Citation

Cai, F., Dou, Z., Bernstein, S. L., Leverenz, R., Williams, E. B., Heinhorst, S., Shively, J. M., Cannon, G. C., Kerfeld, C. A. (2015). Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component. Life, 5(2), 1141-1171.
Available at: https://aquila.usm.edu/fac_pubs/15398