Alkyl sulfatase
| Alkyl sulfatase 1 | ||
|---|---|---|
|
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| Representation of the native protein SdsA1, blue: N-terminal domain, green: dimerization domain, reddish: C-terminal domain, yellow: zinc ions | ||
| Mass / length primary structure | 528 amino acids; 58.9 kDa | |
| Secondary to quaternary structure | Homodimer | |
| Cofactor | 2 Zn 2+ | |
| Identifier | ||
| Gene name (s) | sdsA; sdsA1 | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 3.1.6.- , esterase | |
| Response type | hydrolysis | |
| Substrate | Sulfate ester, dodecyl sulfate | |
| Occurrence | ||
| Homology family | Alkyl sulfatase | |
| Parent taxon | Pseudomonas | |
Alkyl sulfatase ( SdsA1 ) is a protein found in Pseudomonas aeruginosa , a rod bacterium , which belongs to the group of sulfate ester-cleaving enzymes ( sulfatases ).
The name SdsA1 goes back to the fact that the enzyme, in addition to a large number of aliphatic sulfate esters, can also break down the strongly denaturing surfactant sodium dodecyl sulfate (SDS). SdsA1 homologues are found in many pathogenic and some non-pathogenic bacteria. The protein belongs to the third class of sulfatases, which allows Pseudomonas aeruginosa to survive under bactericidal conditions. Significant educational work on the structure and reaction mechanism was carried out by Hagelüken et al. operated.
construction
The protein occurs naturally as a symmetrical homodimer ; it crystallizes in the space group P 6 5 22 (space group no. 179) . Each monomer consists of three protein domains : the N-terminal, catalytically active domain, which is an integral part of a 2-nucleus zinc cluster and belongs to the family of metallo-β-lactamase protein folding ; a dimerization domain, which is responsible for the stability towards the bactericidal SDS, and a C-terminal hydrophobic domain.
Reaction mechanism
The two catalytically active zinc ions are bridged by a common hydroxide ion , which, in contrast to phosphatases, most likely does not function as a nucleophile . As evidence, Hagelüken et al. above all the unusually large distances between the directly bound hydroxide ion and the sulfate group to be cleaved . A second water molecule can be assumed as an alternative nucleophile, which lies exactly between the directly bound hydroxide ion and the sulfate-sulfur atom. This is also coordinated and polarized by the negatively charged amino acid glutamate at position 299 . As a result, the nucleophilicity of the second water molecule is large enough to attack the electrophilic sulfur . After a trigonal-bipyramidal transition state , the leaving alcohol is protonated by the amino acid arginine at position 312 . This ends the cleavage of the sulfate ester to sulfate and the corresponding alcohol and the catalysis can start all over again.
Individual evidence
- ↑ a b Hagelüken et al. (2006): The crystal structure of SdsA1, an alkylsulfatase from Pseudomonas aeruginosa, defines a third class of sulfatases. In: Proc. Natl. Acad. Sci. USA 103 (20): 7631-7636. PMID 16684886