PMID: 19279214 , Related PDB id: 3G43

Authors:

Fallon JL, Baker MR, Xiong L, Loy RE, Yang G, Dirksen RT, Hamilton SL, Quiocho FA

Title:

Crystal structure of dimeric cardiac L-type calcium channel regulatory domains bridged by Ca2+* calmodulins.

Journal:

Proc Natl Acad Sci U S A. 2009 Mar 31;106(13):5135-40. Epub 2009 Mar 11.

Abstract:

Voltage-dependent calcium channels (Ca(V)) open in response to changes in membrane potential, but their activity is modulated by Ca(2+) binding to calmodulin (CaM). Structural studies of this family of channels have focused on CaM bound to the IQ motif; however, the minimal differences between structures cannot adequately describe CaM's role in the regulation of these channels. We report a unique crystal structure of a 77-residue fragment of the Ca(V)1.2 alpha(1) subunit carboxyl terminus, which includes a tandem of the pre-IQ and IQ domains, in complex with Ca(2+).CaM in 2 distinct binding modes. The structure of the Ca(V)1.2 fragment is an unusual dimer of 2 coiled-coiled pre-IQ regions bridged by 2 Ca(2+).CaMs interacting with the pre-IQ regions and a canonical Ca(V)1-IQ-Ca(2+).CaM complex. Native Ca(V)1.2 channels are shown to be a mixture of monomers/dimers and a point mutation in the pre-IQ region predicted to abolish the coiled-coil structure significantly reduces Ca(2+)-dependent inactivation of heterologously expressed Ca(V)1.2 channels.