3GUF

Crystal Structure of the hspA from Xanthomonas axonopodis

Summary for 3GUF

• Entry DOI: 10.2210/pdb3guf/pdb
• Related: 1GME 1SHS 2BOL 3GLA 3GT6 3GTB
• Descriptor: Low molecular weight heat shock protein (2 entities in total)
• Functional Keywords: hspa, shp, shsp, xanthomonas axonopodis, chaperone, small heat shock protein, citrus canker, stress response
• Biological source: Xanthomonas axonopodis pv. citri (Citrus canker)
• Total number of polymer chains: 2
• Total formula weight: 23220.15

Authors

Hilario, E.,Medrano, F.J.,Bertolini, M.C. (deposition date: 2009-03-29, release date: 2011-02-16, Last modification date: 2023-09-06)

Primary citation

Hilario, E.,Martin, F.J.,Bertolini, M.C.,Fan, L.
Crystal structures of Xanthomonas small heat shock protein provide a structural basis for an active molecular chaperone oligomer.
J.Mol.Biol., 408:74-86, 2011

PubMed Abstract: Small heat shock proteins (sHsps) are ubiquitous low-molecular-weight chaperones that prevent protein aggregation under cellular stresses. sHsps contain a structurally conserved α-crystallin domain (ACD) of about 100 amino acid residues flanked by varied N- and C-terminal extensions and usually exist as oligomers. Oligomerization is important for the biological functions of most sHsps. However, the active oligomeric states of sHsps are not defined yet. We present here crystal structures (up to 1.65 Å resolution) of the sHspA from the plant pathogen Xanthomonas (XaHspA). XaHspA forms closed or open trimers of dimers (hexamers) in crystals but exists predominantly as 36mers in solution as estimated by size-exclusion chromatography. The XaHspA monomer structures mainly consist of α-crystallin domain with disordered N- and C-terminal extensions, indicating that the extensions are flexible and not essential for the formation of dimers and 36mers. Under reducing conditions where α-lactalbumin (LA) unfolds and aggregates, XaHspA 36mers formed complexes with one LA per XaHspA dimer. Based on XaHspA dimer-dimer interactions observed in crystals, we propose that XaHspA 36mers have four possible conformations, but only XaHspA 36merB, which is formed by open hexamers in 12mer-6mer-6mer-12mer with protruding dimers accessible for substrate (unfolding protein) binding, can bind to 18 reduced LA molecules. Together, our results unravel the structural basis of an active sHsp oligomer.

PubMed: 21315085
DOI: 10.1016/j.jmb.2011.02.004

Experimental method

X-RAY DIFFRACTION (2.28 Å)