Structure of the SHV-1 beta-lactamase

Area of Science:

• Biochemistry
• Structural Biology
• Crystallography

Background:

• Beta-lactamase enzymes hydrolyze beta-lactam antibiotics, contributing to antibiotic resistance.
• SHV-1 and TEM-1 are clinically significant beta-lactamases with differing inhibitory profiles.
• Understanding their structural basis is crucial for developing new antibiotic strategies.

Purpose of the Study:

• To determine and analyze the X-ray crystallographic structure of the SHV-1 beta-lactamase.
• To compare the structure of SHV-1 with that of TEM-1 beta-lactamase.
• To elucidate the structural basis for differential binding affinities to beta-lactamase inhibitory protein (BLIP).

Main Methods:

• X-ray crystallography was employed to determine the three-dimensional structure of SHV-1 beta-lactamase.
• The crystal structure was solved using molecular replacement and refined to 1.98 A resolution.
• Structural comparison with TEM-1 beta-lactamase was performed using alpha-carbon atom overlays.

Main Results:

• The SHV-1 beta-lactamase structure was refined to an R-factor of 0.18.
• Structural overlay revealed an RMS deviation of 1.4 A between SHV-1 and TEM-1, with variations in the H10 helix and beta-sheet loops.
• SHV-1 possesses a substrate binding cavity 0.7-1.2 A wider than TEM-1, with conserved catalytic site residues.

Conclusions:

• The structural differences, particularly the wider binding cavity in SHV-1, likely contribute to its distinct interactions with BLIP.
• Specific residue interactions, such as those involving Asp/Glu104, are key to understanding SHV-1 and TEM-1 affinity differences for BLIP.
• This structural insight aids in the design of novel beta-lactamase inhibitors.