Q31RK2 · CCMK4_SYNE7
- ProteinCarboxysome shell protein CcmK4
- GeneccmK4
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids113 (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.
A minor shell protein of the carboxysome, a polyhedral inclusion where RuBisCO (ribulose bisphosphate carboxylase, rbcL-rbcS) is sequestered (Probable). Hexamers form sheets that form the facets of the polyhedral carboxysome. The shell is 4.5 nm thick, as observed for CcmK proteins (PubMed:28616951).
In PCC 7942 there are several CcmK paralogs with presumably functional differences; replacing the central pore residues (34-37) with those of CcmK2 from this organism (Tyr-Glu-Lys-Ile) allows the bacterium to make carboxysomes, but the expression level is too low to know if the carboxysome is functional for CO2 fixation (Probable). This subunit probably makes both homohexamers and heterohexamers with CcmK3. The CcmK3-CcmK4 heterohexmers have been suggested to cap other hexamers, perhaps to alter metabolite flux (Probable).
In PCC 7942 there are several CcmK paralogs with presumably functional differences; replacing the central pore residues (34-37) with those of CcmK2 from this organism (Tyr-Glu-Lys-Ile) allows the bacterium to make carboxysomes, but the expression level is too low to know if the carboxysome is functional for CO2 fixation (Probable). This subunit probably makes both homohexamers and heterohexamers with CcmK3. The CcmK3-CcmK4 heterohexmers have been suggested to cap other hexamers, perhaps to alter metabolite flux (Probable).
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. The absence of ccaA, ccmK3, ccmK4, ccmP and rbcX leads to less active RuBisCO.
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 CcmK4
- Alternative names
Gene names
Organism names
- Strain
- Taxonomic lineageBacteria > Cyanobacteriota > Cyanophyceae > Synechococcales > Synechococcaceae > Synechococcus
Accessions
- Primary accessionQ31RK2
Proteomes
Subcellular Location
UniProt Annotation
GO Annotation
Keywords
- Cellular component
Phenotypes & Variants
Disruption phenotype
Single deletion has a wild-type phenotype, a double ccmK3-ccmK4 deletion has slightly larger, aggregated instead of spatially separated carboxysomes, and has a photosynthetic affinity for inorganic carbon between wild-type and carboxysome-less strains (PubMed:22928045).
In another study single mutant grows slower in air and low light, double ccmK3-ccmK4 mutant has similarly impaired growth rate; ccmK3 does not complement the double deletion, while ccmK4 does (PubMed:30389783).
In another study single mutant grows slower in air and low light, double ccmK3-ccmK4 mutant has similarly impaired growth rate; ccmK3 does not complement the double deletion, while ccmK4 does (PubMed:30389783).
Features
Showing features for mutagenesis.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Mutagenesis | 36-38 | Probably alters pore properties, is able to form carboxysomes, residues correspond to CcmK2 of this organism. | ||||
Sequence: MRA → EKI | ||||||
Mutagenesis | 40 | Does not complement its deletion mutant, forms homohexamers in vitro. | ||||
Sequence: S → D |
PTM/Processing
Features
Showing features for chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Chain | PRO_0000451236 | 1-113 | Carboxysome shell protein CcmK4 | |||
Sequence: MSQQAIGSLETKGFPPILAAADAMVKAGRITIVSYMRAGSARFAVNIRGDVSEVKTAMDAGIEAAKNTPGGTLETWVIIPRPHENVEAVFPIGFGPEVEQYRLSAEGTGSGRR |
Proteomic databases
Expression
Induction
Carboxysome size and components vary with growth conditions. When grown in ambient air at medium light (50 uE meter-2 second-1) there are 52 units of this protein per carboxysome, the numbers are stable under low light and high light, and increase under high CO2 (at protein level). The CcmK3:CcmK4 ratio of 1:3.8 is stable over all growth conditions.
Structure
Family & Domains
Features
Showing features for domain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Domain | 5-91 | BMC | ||||
Sequence: AIGSLETKGFPPILAAADAMVKAGRITIVSYMRAGSARFAVNIRGDVSEVKTAMDAGIEAAKNTPGGTLETWVIIPRPHENVEAVFP |
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
- Length113
- Mass (Da)11,946
- Last updated2005-12-06 v1
- ChecksumA961559E472C2545
Keywords
- Technical term
Sequence databases
Nucleotide Sequence | Protein Sequence | Molecule Type | Status | |
---|---|---|---|---|
CP000100 EMBL· GenBank· DDBJ | ABB56317.1 EMBL· GenBank· DDBJ | Genomic DNA |