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Asparagine-84, a regulatory allosteric site residue, helps maintain the quaternary structure of Campylobacter jejuni dihydrodipicolinate synthase

DOI: 10.1016/j.jsb.2019.107409 DOI Help

Authors: Mohadeseh Majdi Yazdi (University of Saskatchewan) , Sagar Saran (University of Saskatchewan) , Tyler Mrozowich (University of Lethbridge) , Cheyanne Lehnert (University of Saskatchewan) , Trushar R. Patel (University of Lethbridge; University of Calgary; University of Alberta) , David A. R. Sanders (University of Saskatchewan) , David R. J. Palmer (University of Saskatchewan)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Structural Biology

State: Published (Approved)
Published: October 2019
Diamond Proposal Number(s): 16028

Abstract: Dihydrodipicolinate synthase (DHDPS) from Campylobacter jejuni is a natively homotetrameric enzyme that catalyzes the first unique reaction of (S)-lysine biosynthesis and is feedback-regulated by lysine through binding to an allosteric site. High-resolution structures of the DHDPS-lysine complex have revealed significant insights into the binding events. One key asparagine residue, N84, makes hydrogen bonds with both the carboxyl and the α-amino group of the bound lysine. We generated two mutants, N84A and N84D, to study the effects of these changes on the allosteric site properties. However, under normal assay conditions, N84A displayed notably lower catalytic activity, and N84D showed no activity. Here we show that these mutations disrupt the quaternary structure of DHDPS in a concentration-dependent fashion, as demonstrated by size-exclusion chromatography, multi-angle light scattering, dynamic light scattering, small-angle X-ray scattering (SAXS) and high-resolution protein crystallography.

Journal Keywords: dihydrodipicolinate synthase; SAXS; X-ray crystallography; quaternary structure; site-directed mutagenesis; allostery

Diamond Keywords: Enzymes

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: B21-High Throughput SAXS

Other Facilities: Canadian Light Source

Added On: 06/11/2019 14:11

Discipline Tags:

Biochemistry Catalysis Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)