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PDBsum entry 5c3c
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Protein binding
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PDB id
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5c3c
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References listed in PDB file
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Key reference
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Title
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Structural characterization of a newly identified component of α-Carboxysomes: the aaa+ domain protein csocbbq.
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Authors
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M.Sutter,
E.W.Roberts,
R.C.Gonzalez,
C.Bates,
S.Dawoud,
K.Landry,
G.C.Cannon,
S.Heinhorst,
C.A.Kerfeld.
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Ref.
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Sci Rep, 2015,
5,
16243.
[DOI no: ]
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PubMed id
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Abstract
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Carboxysomes are bacterial microcompartments that enhance carbon fixation by
concentrating ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and its
substrate CO2 within a proteinaceous shell. They are found in all cyanobacteria,
some purple photoautotrophs and many chemoautotrophic bacteria. Carboxysomes
consist of a protein shell that encapsulates several hundred molecules of
RuBisCO, and contain carbonic anhydrase and other accessory proteins. Genes
coding for carboxysome shell components and the encapsulated proteins are
typically found together in an operon. The α-carboxysome operon is embedded in
a cluster of additional, conserved genes that are presumably related to its
function. In many chemoautotrophs, products of the expanded carboxysome locus
include CbbO and CbbQ, a member of the AAA+ domain superfamily. We
bioinformatically identified subtypes of CbbQ proteins and show that their genes
frequently co-occur with both Form IA and Form II RuBisCO. The
α-carboxysome-associated ortholog, CsoCbbQ, from Halothiobacillus neapolitanus
forms a hexamer in solution and hydrolyzes ATP. The crystal structure shows that
CsoCbbQ is a hexamer of the typical AAA+ domain; the additional C-terminal
domain, diagnostic of the CbbQ subfamily, structurally fills the inter-monomer
gaps, resulting in a distinctly hexagonal shape. We show that CsoCbbQ interacts
with CsoCbbO and is a component of the carboxysome shell, the first example of
ATPase activity associated with a bacterial microcompartment.
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