PDBsum entry 2vay

Metal transport

PDB id: 2vay

Contents

Protein chains

146 a.a.

21 a.a.

Metals

_CA ×4

_CL

Waters ×127

References listed in PDB file

Key reference

Title

Determinants in cav1 channels that regulate the ca2+ sensitivity of bound calmodulin.

Authors

D.B.Halling, D.K.Georgiou, D.J.Black, G.Yang, J.L.Fallon, F.A.Quiocho, S.E.Pedersen, S.L.Hamilton.

Ref.

J Biol Chem, 2009, 284, 20041-20051. [DOI no: 10.1074/jbc.M109.013326]

PubMed id

19473981

Abstract

Calmodulin binds to IQ motifs in the alpha(1) subunit of Ca(V)1.1 and Ca(V)1.2, but the affinities of calmodulin for the motif and for Ca(2+) are higher when bound to Ca(V)1.2 IQ. The Ca(V)1.1 IQ and Ca(V)1.2 IQ sequences differ by four amino acids. We determined the structure of calmodulin bound to Ca(V)1.1 IQ and compared it with that of calmodulin bound to Ca(V)1.2 IQ. Four methionines in Ca(2+)-calmodulin form a hydrophobic binding pocket for the peptide, but only one of the four nonconserved amino acids (His-1532 of Ca(V)1.1 and Tyr-1675 of Ca(V)1.2) contacts this calmodulin pocket. However, Tyr-1675 in Ca(V)1.2 contributes only modestly to the higher affinity of this peptide for calmodulin; the other three amino acids in Ca(V)1.2 contribute significantly to the difference in the Ca(2+) affinity of the bound calmodulin despite having no direct contact with calmodulin. Those residues appear to allow an interaction with calmodulin with one lobe Ca(2+)-bound and one lobe Ca(2+)-free. Our data also provide evidence for lobe-lobe interactions in calmodulin bound to Ca(V)1.2.

Figure 1.
Structure of CaM bound to Ca[V]1.1 IQ (PDB code 2vay) is represented in A–C. Structure of previously solved CaM bound to Ca[V]1.2 IQ was obtained from the PDB with accession number 2f3y (d–F). Ribbon schematics represent CaM bound to Ca[V]1.1 IQ in A or to Ca[V]1.2 IQ in D. Peptides are represented as green ribbons. Ca^2+ ions are represented as yellow spheres. The amino terminus (N) of the peptide contacts the N-lobe (pink ribbon) of CaM. C-lobe of CaM is blue. Linker ribbons that join the lobes of CaM are light gray. Residues of Ca[V]1.1 IQ motif that are different from Ca[V]1.2 IQ are represented as sticks on peptide ribbon, except for the residues not observed in the structure. B and E depict peptide stick residues contacting molecular surface of the N-lobe. C and F show peptide residue side chains (shown as sticks) in the vicinity of the C-lobe hydrophobic pocket formed by methionines (shown as molecular surface). B, C, E, and F, N-lobe carbons are pink, and carbon atoms in the linker between N- and C-lobes of CaM are light gray; C-lobe carbons are light blue (teal); peptide carbons are green; oxygen atoms are red; sulfur atoms are orange; nitrogen atoms are dark blue; waters are marine spheres; speculated chloride is green sphere. The 2F[o] − F[c] maps representing electron density are blue meshes. For best visibility, the 2vay 2F[o] − F[c] map is at 1.0 Å threshold and 2f3y map is at presented 0.5 Å.

Figure 4.
Effect of blocking Ca^2+ binding to a single lobe on the K[D][,app] of CaM for Ca^2+ when bound to peptide. All data were collected in triplicate as the mean ± S.D. A, 1 μm F19W/E34Q alone (closed circles) or with 5 μm Ca[V]1.1 IQ (open circles) or with 5 μm Ca[V]1.2 IQ (closed diamonds). All data are fit with standard sigmoid curve. Long dashes, fit for F19W/Ca[V]1.2 IQ shown previously (1); dash-dot-dot, fit for F19W/Ca[V]1.1 IQ from Fig. 3. B, 1 μm F92W/E12Q alone (closed circles) or with 5 μm Ca[V]1.1 IQ (open circles) are plotted. Long dashes, fit for F92W/Ca[V]1.2 IQ shown previously (1); dash-dot-dot, fit for F92W/Ca[V]1.1 IQ from Fig. 3; dotted line, fit for F92WE12Q/Ca[V]1.2 IQ shown previously (1).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2009, 284, 20041-20051) copyright 2009.