The Journal of antimicrobial chemotherapy · 2015
Structural insights into the loss of penicillinase and the gain of ceftazidimase activities by OXA-145 β-lactamase in Pseudomonas aeruginosa.
СтатьяПоддержка исследования: вне правительства СШАНазвание и аннотация: Перевод в очереди
Обработка статьи · этапы, ошибки и управление
Загрузка состояния…
Ошибки и ограничения
История · было → стало
Состояние обновляется каждые 5 секунд, пока блок открыт. Процент показывается только там, где известен объём работы. Пауза останавливает продолжение этапа; текущий запрос к источнику может завершиться.
Meziane-Cherif D, Bonnet R, Haouz A, Courvalin P
Аннотация
OBJECTIVES: We previously described extended-spectrum oxacillinase OXA-145 from Pseudomonas aeruginosa, which differs from narrow-spectrum OXA-35 by loss of Leu-155. The deletion results in loss of benzylpenicillin hydrolysis and acquisition of activity against ceftazidime. We report the crystal structure of OXA-145 and provide the basis of its switch in substrate specificity.
METHODS: OXA-145 variants were generated by site-directed mutagenesis and purified to homogeneity. The crystal structure of OXA-145 was determined and molecular dynamics simulations were performed. Kinetic parameters were investigated in the absence and in the presence of sodium hydrogen carbonate (NaHCO3) for representative substrates.
RESULTS: The structure of OXA-145 was obtained at a resolution of 2.3 Å and its superposition with that of OXA-10 showed that Trp-154 was shifted by 1.8 Å away from the catalytic Lys-70, which was not N-carboxylated. Addition of NaHCO3 significantly increased the catalytic efficiency against penicillins, but not against ceftazidime. The active-site cavity of OXA-145 was larger than that of OXA-10, which may favour the accommodation of large molecules such as ceftazidime. Molecular dynamics simulations of OXA-145 in complex with ceftazidime revealed two highly coordinated water molecules on the α- or β-face of the acyl ester bond, between Ser-67 and ceftazidime, which could be involved in the catalytic process.
CONCLUSIONS: Deletion of Leu-155 resulted in inefficient positioning of Trp-154, leading to a non-carboxylated Lys-70 and thus to loss of hydrolysis of the penicillins. Ceftazidime hydrolysis could be attributed to enlargement of the active site and to a catalytic mechanism independent of the carboxylated Lys-70.
METHODS: OXA-145 variants were generated by site-directed mutagenesis and purified to homogeneity. The crystal structure of OXA-145 was determined and molecular dynamics simulations were performed. Kinetic parameters were investigated in the absence and in the presence of sodium hydrogen carbonate (NaHCO3) for representative substrates.
RESULTS: The structure of OXA-145 was obtained at a resolution of 2.3 Å and its superposition with that of OXA-10 showed that Trp-154 was shifted by 1.8 Å away from the catalytic Lys-70, which was not N-carboxylated. Addition of NaHCO3 significantly increased the catalytic efficiency against penicillins, but not against ceftazidime. The active-site cavity of OXA-145 was larger than that of OXA-10, which may favour the accommodation of large molecules such as ceftazidime. Molecular dynamics simulations of OXA-145 in complex with ceftazidime revealed two highly coordinated water molecules on the α- or β-face of the acyl ester bond, between Ser-67 and ceftazidime, which could be involved in the catalytic process.
CONCLUSIONS: Deletion of Leu-155 resulted in inefficient positioning of Trp-154, leading to a non-carboxylated Lys-70 and thus to loss of hydrolysis of the penicillins. Ceftazidime hydrolysis could be attributed to enlargement of the active site and to a catalytic mechanism independent of the carboxylated Lys-70.