3IQA

Crystal Structure of BlaC covalently bound with Doripenem

Summary for 3IQA

• Entry DOI: 10.2210/pdb3iqa/pdb
• Descriptor: Beta-lactamase, PHOSPHATE ION, (2S,3R,4S)-2-[(2S,3R)-3-hydroxy-1-oxobutan-2-yl]-3-methyl-4-({(3S,5S)-5-[(sulfamoylamino)methyl]pyrrolidin-3-yl}sulfanyl)-3,4-dihydro-2H-pyrrole-5-carboxylic acid, ... (4 entities in total)
• Functional Keywords: penicillin binding protein, beta-lactam covalent adduct, antibiotic resistance, cell membrane, hydrolase, lipoprotein, membrane, palmitate, hydrolase-hydrolase inhibitor complex, hydrolase/hydrolase inhibitor
• Biological source: Mycobacterium tuberculosis
• Total number of polymer chains: 1
• Total formula weight: 28885.18

Authors

Tremblay, L.W.,Blanchard, J.S. (deposition date: 2009-08-19, release date: 2010-04-14, Last modification date: 2024-11-06)

Primary citation

Tremblay, L.W.,Fan, F.,Blanchard, J.S.
Biochemical and structural characterization of Mycobacterium tuberculosis beta-lactamase with the carbapenems ertapenem and doripenem.
Biochemistry, 49:3766-3773, 2010

PubMed Abstract: Despite the enormous success of beta-lactams as broad-spectrum antibacterials, they have never been widely used for the treatment of tuberculosis (TB) due to intrinsic resistance that is caused by the presence of a chromosomally encoded gene (blaC) in Mycobacterium tuberculosis. Our previous studies of TB BlaC revealed that this enzyme is an extremely broad-spectrum beta-lactamase hydrolyzing all beta-lactam classes. Carbapenems are slow substrates that acylate the enzyme but are only slowly deacylated and can therefore act also as potent inhibitors of BlaC. We conducted the in vitro characterization of doripenem and ertapenem with BlaC. A steady-state kinetic burst was observed with both compounds with magnitudes proportional to the concentration of BlaC used. The results provide apparent K(m) and k(cat) values of 0.18 microM and 0.016 min(-1) for doripenem and 0.18 microM and 0.017 min(-1) for ertapenem, respectively. FTICR mass spectrometry demonstrated that the doripenem and ertapenem acyl-enzyme complexes remain stable over a time period of 90 min. The BlaC-doripenem covalent complex obtained after a 90 min soak was determined to 2.2 A, while the BlaC-ertapenem complex obtained after a 90 min soak was determined to 2.0 A. The 1.3 A diffraction data from a 10 min ertapenem-soaked crystal revealed an isomerization occurring in the BlaC-ertapenem adduct in which the original Delta(2)-pyrroline ring was tautomerized to generate the Delta(1)-pyrroline ring. The isomerization leads to the flipping of the carbapenem hydroxyethyl group to hydrogen bond to carboxyl O2 of Glu166. The hydroxyethyl flip results in both the decreased basicity of Glu166 and a significant increase in the distance between carboxyl O2 of Glu166 and the catalytic water molecule, slowing hydrolysis.

PubMed: 20353175
DOI: 10.1021/bi100232q

Experimental method

X-RAY DIFFRACTION (2.2 Å)