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Characterization of amplified esterase Estβ1 2 associated with organophosphate resistance in a multi‐resistant population of the mosquito Culex quinquefasciatus from Cuba
Author(s) -
Karunaratne,
Janet Hemingway
Publication year - 1998
Publication title -
medical and veterinary entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 82
eISSN - 1365-2915
pISSN - 0269-283X
DOI - 10.1046/j.1365-2915.1998.00100.x
Subject(s) - biology , esterase , amplicon , culex quinquefasciatus , population , culex , microbiology and biotechnology , insecticide resistance , pesticide resistance , enzyme , genetics , toxicology , pesticide , biochemistry , gene , polymerase chain reaction , ecology , larva , aedes aegypti , demography , sociology
Esterase amplification is the major organophosphorus (OP) insecticide resistance mechanism in Culex mosquitoes. The amplified Estα2 1\ Estβ2 1 esterases are found in > 90% of resistant populations worldwide, whereas amplified DNAs (amplicons) containing Estβ1s are much rarer. Individuals with the Estβ1 amplicons appear to be at a selective disadvantage in competition with those carrying the Estα2 1 \ Estβ2 1 amplicons. To test the hypothesis that this is because Estβ1 is less able to bind insecticide than the common amplified esterases, Estβ1 2 was purified from the multi‐resistant Habana strain of Culex quinquefasciatus , from Cuba. In its native form Estβ1 is a monomeric enzyme of 66 kDa, with a pI of 4.8. The bimolecular rate constants for interaction of Estβ1 2 with several OP insecticides were similar to those for the commonly elevated esterases Estα2 1 and Estβ2 1 , and much higher than for the electrophoretically identical non‐elevated Estβ1 3 and Estα3. Hence the apparent selective advantage of the Estα2 1 \ Estβ2 1 amplicon is not due to its greater efficiency of insecticide binding, as OP insecticides are significantly better inhibitors of all the amplified esterases than of their non‐amplified counterparts and therefore should be equally effective at conferring resistance.