2LVK

Solution structure of Ca-bound Phl p 7

Summary for 2LVK

• Entry DOI: 10.2210/pdb2lvk/pdb
• Related: 2LVI 2LVJ
• NMR Information: BMRB: 18573
• Descriptor: Polcalcin Phl p 7, CALCIUM ION (2 entities in total)
• Functional Keywords: ef-hand protein, calcium-binding protein, allergen
• Biological source: Phleum pratense (timothy)
• Total number of polymer chains: 1
• Total formula weight: 8633.65

Authors

Henzl, M.T.,Sirianni, A.G.,Tanner, J.J. (deposition date: 2012-07-05, release date: 2012-10-03, Last modification date: 2024-05-15)

Primary citation

Henzl, M.T.,Sirianni, A.G.,Wycoff, W.G.,Tan, A.,Tanner, J.J.
Solution structures of polcalcin Phl p 7 in three ligation states: Apo-, hemi-Mg(2+) -bound, and fully Ca(2+) -bound.
Proteins, 81:300-315, 2013

PubMed Abstract: Polcalcins are small EF-hand proteins believed to assist in regulating pollen-tube growth. Phl p 7, from timothy grass (Phleum pratense), crystallizes as a domain-swapped dimer at low pH. This study describes the solution structures of the recombinant protein in buffered saline at pH 6.0, containing either 5.0 mM EDTA, 5.0 mM Mg(2+), or 100 μM Ca(2+). Phl p 7 is monomeric in all three ligation states. In the apo-form, both EF-hand motifs reside in the closed conformation, with roughly antiparallel N- and C-terminal helical segments. In 5.0 mM Mg(2+), the divalent ion is bound by EF-hand 2, perturbing interhelical angles and imposing more regular helical structure. The structure of Ca(2+)-bound Phl p 7 resembles that previously reported for Bet v 4-likewise exposing apolar surface to the solvent. Occluded in the apo- and Mg(2+)-bound forms, this surface presumably provides the docking site for Phl p 7 targets. Unlike Bet v 4, EF-hand 2 in Phl p 7 includes five potential anionic ligands, due to replacement of the consensus serine residue at -x (residue 55 in Phl p 7) with aspartate. In the Phl p 7 crystal structure, D55 functions as a helix cap for helix D. In solution, however, D55 apparently serves as a ligand to the bound Ca(2+). When Mg(2+) resides in site 2, the D55 carboxylate withdraws to a distance consistent with a role as an outer-sphere ligand. (15)N relaxation data, collected at 600 MHz, indicate that backbone mobility is limited in all three ligation states.

PubMed: 23011803
DOI: 10.1002/prot.24186

Experimental method

SOLUTION NMR