5W1U

Culex quinquefasciatus carboxylesterase B2

Summary for 5W1U

• Entry DOI: 10.2210/pdb5w1u/pdb
• Descriptor: Carboxylic ester hydrolase, 4-(2-HYDROXYETHYL)-1-PIPERAZINE ETHANESULFONIC ACID, MALONATE ION, ... (4 entities in total)
• Functional Keywords: carboxylesterase, alpha/beta hydrolase, hydrolase
• Biological source: Culex quinquefasciatus (Southern house mosquito)
• Total number of polymer chains: 2
• Total formula weight: 122206.85

Authors

Hopkins, D.H.,Jackson, C.J. (deposition date: 2017-06-04, release date: 2017-08-16, Last modification date: 2024-03-13)

Primary citation

Hopkins, D.H.,Fraser, N.J.,Mabbitt, P.D.,Carr, P.D.,Oakeshott, J.G.,Jackson, C.J.
Structure of an Insecticide Sequestering Carboxylesterase from the Disease Vector Culex quinquefasciatus: What Makes an Enzyme a Good Insecticide Sponge?
Biochemistry, 56:5512-5525, 2017

PubMed Abstract: Carboxylesterase (CBE)-mediated metabolic resistance to organophosphate and carbamate insecticides is a major problem for the control of insect disease vectors, such as the mosquito. The most common mechanism involves overexpression of CBEs that bind to the insecticide with high affinity, thereby sequestering them before they can interact with their target. However, the absence of any structure for an insecticide-sequestering CBE limits our understanding of the molecular basis for this process. We present the first structure of a CBE involved in sequestration, Cqestβ2, from the mosquito disease vector Culex quinquefasciatus. Lysine methylation was used to obtain the crystal structure of Cqestβ2, which adopts a canonical α/β-hydrolase fold that has high similarity to the target of organophosphate and carbamate insecticides, acetylcholinesterase. Sequence similarity networks of the insect carboxyl/cholinesterase family demonstrate that CBEs associated with metabolic insecticide resistance across many species share a level of similarity that distinguishes them from a variety of other classes. This is further emphasized by the structural similarities and differences in the binding pocket and active site residues of Cqestβ2 and other insect carboxyl/cholinesterases. Stopped-flow and steady-state inhibition studies support a major role for Cqestβ2 in organophosphate resistance and a minor role in carbamate resistance. Comparison with another isoform associated with insecticide resistance, Cqestβ1, showed both enzymes have similar affinity to insecticides, despite 16 amino acid differences between the two proteins. This provides a molecular understanding of pesticide sequestration by insect CBEs and could facilitate the design of CBE-specific inhibitors to circumvent this resistance mechanism in the future.

PubMed: 28929747
DOI: 10.1021/acs.biochem.7b00774

Experimental method

X-RAY DIFFRACTION (2.5 Å)