title: Theoretical Study of the Initial Stages of Self-Assembly of a Carboxysome's Facet.
abstract: Bacterial microcompartments, BMCs, are organelles that exist within wide variety of bacteria and act as nanofactories. Among the different types of known BMCs, the carboxysome has been studied the most. The carboxysome plays an important role in the light-independent part of the photosynthesis process, where its icosahedral-like proteinaceous shell acts as a membrane that controls the transport of metabolites. Although a structural model exists for the carboxysome shell, it remains largely unknown how the shell proteins self-assemble. Understanding the self-assembly process can provide insights into how the shell affects the carboxysome's function and how it can be modified to create new functionalities, such as artificial nanoreactors and artificial protein membranes. Here, we describe a theoretical framework that employs Monte Carlo simulations with a coarse-grain potential that reproduces well the atomistic potential of mean force; employing this framework, we are able to capture the initial stages of the 2D self-assembly of CcmK2 hexamers, a major protein-shell component of the carboxysome's facet. The simulations reveal that CcmK2 hexamers self-assemble into clusters that resemble what was seen experimentally in 2D layers. Further analysis of the simulation results suggests that the 2D self-assembly of carboxysome's facets is driven by a nucleation-growth process, which in turn could play an important role in the hierarchical self-assembly of BMC shells in general.
authors.forename: J P
authors.initials: JP
authors.lastname: Mahalik
authors.affiliation: Chemistry Department, Mercer University , 1501 Mercer University Drive, Macon, Georgia 31207, United States.
authors.forename: Kirsten A
authors.initials: KA
authors.lastname: Brown
authors.affiliation: Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee , M407 Walters Life Sciences, 1414 Cumberland Avenue, Knoxville, Tennessee 37996, United States.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cheng
authors.forename: Miguel
authors.initials: M
authors.lastname: Fuentes-Cabrera
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D000458:Cyanobacteria / Q000648:ultrastructure*; D008958:Models, Molecular; D009010:Monte Carlo Method; D015388:Organelles / Q000737:chemistry*; D066329:Protein Aggregates; D011487:Protein Conformation; D055503:Protein Multimerization
chemical_list: D001426:Bacterial Proteins; D066329:Protein Aggregates
keywords: all-atomistic; carboxysome; coarse-grain model; nucleation−growth; potential of mean force; protein self-assembly