1s3p
From Proteopedia
|
Crystal structure of rat alpha-parvalbumin S55D/E59D mutant
Overview
In model peptide systems, Ca2+ affinity is maximized in EF-hand motifs, containing four carboxylates positioned on the +x and -x and +z and -z, axes; introduction of a fifth carboxylate ligand reduces the affinity., However, in rat beta-parvalbumin, replacement of Ser-55 with aspartate, heightens divalent ion affinity [Henzl, M. T., et al. (1996) Biochemistry, 35, 5856-5869]. The corresponding alpha-parvalbumin variant (S55D/E59D), likewise exhibits elevated affinity [Henzl, M. T., et al. (2003) Anal., Biochem. 319, 216-233]. To determine whether these mutations produce a, variation on the archetypal EF-hand coordination scheme, we have obtained, high-resolution X-ray crystallographic data for alpha S55D/E59D. As, anticipated, the aspartyl carboxylate replaces the serine hydroxyl at the, +z coordination position. Interestingly, the Asp-59 carboxylate abandons, the role it plays as an outer sphere ligand in wild-type rat beta, rotating away from the Ca2+ and, instead, forming a hydrogen bond with the, amide of Glu-62. Superficially, the coordination sphere in the CD site of, alpha S55D/E59D resembles that in the EF site. However, the orientation of, the Asp-59 side chain is predicted to stabilize the D-helix, which may, contribute to the heightened divalent ion affinity. DSC data indicate that, the alpha S55D/E59D variant retains the capacity to bind 1 equiv of Na+., Consistent with this finding, when binding measurements are conducted in, K(+)-containing buffer, divalent ion affinity is markedly higher. In 0.15, M KCl and 0.025 M Hepes-KOH (pH 7.4) at 5 degrees C, the macroscopic Ca2+, binding constants are 1.8 x 10(10) and 2.0 x 10(9) M(-1). The, corresponding Mg2+ binding constants are 2.7 x 10(6) and 1.2 x 10(5), M(-1).
About this Structure
1S3P is a Single protein structure of sequence from Rattus norvegicus with CA and SO4 as ligands. Full crystallographic information is available from OCA.
Reference
Crystal structure of a high-affinity variant of rat alpha-parvalbumin., Lee YH, Tanner JJ, Larson JD, Henzl MT, Biochemistry. 2004 Aug 10;43(31):10008-17. PMID:15287728
Page seeded by OCA on Wed Nov 21 02:04:42 2007
