Q03511 · CCMK2_SYNE7
- ProteinCarboxysome shell protein CcmK2
- GeneccmK2
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids102 (go to sequence)
- Protein existenceEvidence at protein level
- Annotation score5/5
Function
function
One of the shell proteins of the carboxysome, a polyhedral inclusion where RuBisCO (ribulose bisphosphate carboxylase, rbcL-rbcS) is sequestered. Assembles into hexamers which make sheets that form the facets of the polyhedral carboxysome. The hexamer central pore probably regulates metabolite flux.
The major shell protein of the carboxysome, a polyhedral inclusion where RuBisCO (ribulose bisphosphate carboxylase, rbcL-rbcS) is sequestered. Hexamers make sheets that form the facets of the polyhedral carboxysome (PubMed:22928045).
The shell is 4.5 nm thick, as observed for CcmK hexamers (PubMed:28616951).
Required for recruitment of CcmO to the pre-carboxysome (PubMed:22928045, PubMed:24267892).
In PCC 7942 there are several CcmK paralogs with presumably functional differences; replacing the central pore residues (34-37) with those of either CcmK4 from this organism (Tyr-Met-Arg-Ala) or from an alpha-type carboxysome forming cyanobacterium (CsoS1 of P.marinus strain MIT 9313, Arg-Glu-Phe-Val) allows the bacterium to make carboxysomes, but the expression level is too low to know if the carboxysome is functional for CO2 fixation (PubMed:25117559).
The shell is 4.5 nm thick, as observed for CcmK hexamers (PubMed:28616951).
Required for recruitment of CcmO to the pre-carboxysome (PubMed:22928045, PubMed:24267892).
In PCC 7942 there are several CcmK paralogs with presumably functional differences; replacing the central pore residues (34-37) with those of either CcmK4 from this organism (Tyr-Met-Arg-Ala) or from an alpha-type carboxysome forming cyanobacterium (CsoS1 of P.marinus strain MIT 9313, Arg-Glu-Phe-Val) allows the bacterium to make carboxysomes, but the expression level is too low to know if the carboxysome is functional for CO2 fixation (PubMed:25117559).
Beta-carboxysome assembly initiates when soluble RuBisCO is condensed into a liquid matrix in a pre-carboxysome by the RbcS-like domains of probably both CcmM58 and CcmM35. CcmN interacts with the N-terminus of CcmM58, and then recruits the CcmK2 major shell protein via CcmN's encapsulation peptide. Shell formation requires CcmK proteins and CcmO. CcmL caps the otherwise elongated carboxysome. Once fully encapsulated carboxysomes are formed, they migrate within the cell probably via interactions with the cytoskeleton.
Biotechnology
Heterologous expression of 12 carboxysomal genes in E.coli (ccaA, ccmK2, ccmK3, ccmK4, ccmL, ccmM, ccmN, ccmO, ccmP, rbcL, rbcS, rbcX) leads to the formation of bodies that resemble carboxysomes, have densely packed paracrystalline arrays and RuBisCO activity. These structures open the door to generating carboxysomes in plant cells to increase their photosynthesis and productivity, as well as tailoring bacterial microcompartments to specific metabolic needs and molecule delivery.
GO annotations
Aspect | Term | |
---|---|---|
Cellular Component | carboxysome | |
Molecular Function | structural constituent of carboxysome shell | |
Biological Process | carbon fixation | |
Biological Process | photosynthesis |
Keywords
- Biological process
Enzyme and pathway databases
Names & Taxonomy
Protein names
- Recommended nameCarboxysome shell protein CcmK2
- Alternative names
Gene names
Organism names
- Strain
- Taxonomic lineageBacteria > Cyanobacteriota > Cyanophyceae > Synechococcales > Synechococcaceae > Synechococcus
Accessions
- Primary accessionQ03511
- Secondary accessions
Proteomes
Subcellular Location
UniProt Annotation
GO Annotation
Note: This cyanobacterium makes beta-type carboxysomes.
Keywords
- Cellular component
Phenotypes & Variants
Disruption phenotype
Cells do not grow in normal air but do grow on 2% CO2, called a high-CO2 requiring phenotype, HCR (PubMed:22928045, PubMed:8491708).
Cells make aberrantly large polar bodies instead of wild-type carboxysomes, no accumulation of CcmO (PubMed:22928045, PubMed:24267892).
An alternatively generated deletion mutant does not form abnormal polar bodies (PubMed:25117559).
Cells make aberrantly large polar bodies instead of wild-type carboxysomes, no accumulation of CcmO (PubMed:22928045, PubMed:24267892).
An alternatively generated deletion mutant does not form abnormal polar bodies (PubMed:25117559).
Features
Showing features for mutagenesis.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Mutagenesis | 34-37 | Probably alters pore properties, is able to form carboxysomes, residues correspond to CsoS1 of P.marinus MIT 9313. | ||||
Sequence: YEKI → REFV | ||||||
Mutagenesis | 35-37 | Probably alters pore properties, is able to form carboxysomes, residues correspond to CcmK4 of this organism. | ||||
Sequence: EKI → MRA |
PTM/Processing
Features
Showing features for chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Chain | PRO_0000201503 | 1-102 | Carboxysome shell protein CcmK2 | |||
Sequence: MPIAVGMIETLGFPAVVEAADAMVKAARVTLVGYEKIGSGRVTVIVRGDVSEVQASVSAGLDSAKRVAGGEVLSHHIIARPHENLEYVLPIRYTEAVEQFRM |
Proteomic databases
Structure
Family & Domains
Features
Showing features for domain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Domain | 4-90 | BMC | ||||
Sequence: AVGMIETLGFPAVVEAADAMVKAARVTLVGYEKIGSGRVTVIVRGDVSEVQASVSAGLDSAKRVAGGEVLSHHIIARPHENLEYVLP |
Domain
The tight homohexamer forms a pore with an opening of about 5 Angstroms in diameter and is positively charged.
Sequence similarities
Belongs to the bacterial microcompartments protein family. CcmK subfamily.
Phylogenomic databases
Family and domain databases
Sequence
- Sequence statusComplete
- Length102
- Mass (Da)10,904
- Last updated1993-10-01 v1
- Checksum7B7C0F5A3D1E1CB7
Keywords
- Technical term
Sequence databases
Nucleotide Sequence | Protein Sequence | Molecule Type | Status | |
---|---|---|---|---|
M96929 EMBL· GenBank· DDBJ | AAA27304.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
CP000100 EMBL· GenBank· DDBJ | ABB57451.1 EMBL· GenBank· DDBJ | Genomic DNA |