Database accession: MF7000279
Name: Beta-carbonic anhydrase CafC (L25G and L78G mutant)
PDB ID: 6jqd
Experimental method: X-ray (1.69 Å)
Assembly: Homodimer
Source organism: Aspergillus fumigatus
Primary publication of the structure:
Kim S, Kim NJ, Hong S, Kim S, Sung J, Jin MS
The structural basis of the low catalytic activities of the two minor β-carbonic anhydrases of the filamentous fungus Aspergillus fumigatus.
(2019) J. Struct. Biol. 208: 61-68
PMID: 31376470
Abstract:
The β-carbonic anhydrases (β-CAs) are widely distributed zinc-metalloenzymes that play essential roles in growth, survival, development and virulence in fungi. The majority of filamentous ascomycetes possess multiple β-CA isoforms among which major and minor forms have been characterized. We examined the catalytic behavior of the two minor β-CAs, CafC and CafD, of Aspergillus fumigatus, and found that both enzymes exhibited low CO2 hydration activities. To understand the structural basis of their low activities, we performed X-ray crystallographic and site-directed mutagenesis studies. Both enzymes exist as homodimers. Like other Type-I β-CAs, the CafC active site has an "open" conformation in which the zinc ion is tetrahedrally coordinated by three residues (C36, H88 and C91) and a water molecule. However, L25 and L78 on the rim of the catalytic entry site protrude into the active site cleft, partially occluding access to it. Single (L25G or L78G) and double mutants provided evidence that widening the entrance to the active site greatly accelerates catalytic activity. By contrast, CafD has a typical Type-II "closed" conformation in which the zinc-bound water molecule is replaced by aspartic acid (D36). The most likely explanation for this result is that an arginine that is largely conserved within the β-CA family is replaced by glycine (G38), so that D36 cannot undergo a conformational change by forming a D-R pair that creates the space for a zinc-bound water molecule and switches the enzyme to the active form. The CafD structure also reveals the presence of a "non-catalytic" zinc ion in the dimer interface, which may contribute to stabilizing the dimeric assembly.
Annotations from the GeneOntology database. Only terms that fit at least two of the interacting proteins are shown. Molecular function:
carbonate dehydratase activity carbonate dehydratase activity
zinc ion binding zinc ion binding
Biological process: not assigned
Cellular component: not assigned
Structural annotations of the participating protein chains.Entry contents: 2 distinct polypeptide molecules
Chains: A, B
Notes: All chains according to the most probable oligomerization state stored in PDBe were considered.
Number of unique protein segments: 1
Name: Carbonic anhydrase
Source organism: Aspergillus fumigatus
Length: 165 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMTNVADIEAANAQYAAAFTKGHLPLPPKRKLAVVTCMDARIDVFSVLGLTEGDAHVIRNAGGRASEALRSLIISQRLLGTEEVVVIHHTDCGMLTFSDEDIRAKIREELGEDASDIKFLPFRDLEASVREDVRFLRGSRLVQGNVTGYVYEVERGRLVRLDVSDI
UniProtKB AC: Q4WPJ0 (positions: 1-164)
Coverage: 99%
Name: Carbonic anhydrase
Source organism: Aspergillus fumigatus
Length: 165 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMTNVADIEAANAQYAAAFTKGHLPLPPKRKLAVVTCMDARIDVFSVLGLTEGDAHVIRNAGGRASEALRSLIISQRLLGTEEVVVIHHTDCGMLTFSDEDIRAKIREELGEDASDIKFLPFRDLEASVREDVRFLRGSRLVQGNVTGYVYEVERGRLVRLDVSDI
UniProtKB AC: Q4WPJ0 (positions: 1-164)
Coverage: 99%
Evidence demonstrating that the participating proteins are unstructured prior to the interaction and their folding is coupled to binding. Representative domain in related structures: Carbonic anhydrase
Evidence level: Indirect evidence
Evidence coverage: The full structure participates in mutual synergistic folding.
Complex Evidence:
The native carbonic anhydrase is dimeric in solution, in agreement with being a tightly associated dimer with a large, hydrophobic buried surface area. The extended β-sheet core consisting of ten β–strands is equally contributed by the two monomers, and the N-terminal helix of each monomer extends around the other monomer. Based on the highly intertwined structure, the monomeric form is most probably not a stable, independently folding unit. The two active sites are also located in clefts at the dimeric interface, further suggesting that dimer is the functional form (PMID:32515610).
Chain A:
N/A
Chain B:
N/A
Surface and contacts features:
Structures from the PDB that contain the same number of proteins, and the proteins from the two structures show a sufficient degree of pairwise similarity, i.e. they belong to the same UniRef90 cluster (the full proteins exhibit at least 90% sequence identity) and convey roughly the same region to their respective interactions (the two regions from the two proteins share a minimum of 70% overlap). Download the CIF file (.cif)
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