CaMBD

Calmodulin binding domain

• SMART accession number: SM01053
• Description: Small-conductance Ca2+-activated K+ channels (SK channels) are independent of voltage and gated solely by intracellular Ca2+. These membrane channels are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM) (PUBMED:11323678). CaM binds to the SK channel through this the CaM-binding domain (CaMBD), which is located in an intracellular region of the alpha-subunit immediately carboxy-terminal to the pore. Channel opening is triggered when Ca2+ binds the EF hands in the N-lobe of CaM. The structure of this domain complexed with CaM is known (PUBMED:11323678). This domain forms an elongated dimer with a CaM molecule bound at each end; each CaM wraps around three alpha-helices, two from one CaMBD subunit and one from the other.
• Interpro abstract (IPR004178):

  Small-conductance Ca2+-activated K+ channels (SK channels) are independent of voltage and gated solely by intracellular Ca2+. These membrane channels are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM) [ (PUBMED:11323678) ]. CaM binds to the SK channel through this the CaM-binding domain (CaMBD), which is located in an intracellular region of the alpha-subunit immediately carboxy-terminal to the pore. Channel opening is triggered when Ca2+ binds the EF hands in the N-lobe of CaM. The structure of this domain complexed with CaM is known [ (PUBMED:11323678) ]. This domain forms an elongated dimer with a CaM molecule bound at each end; each CaM wraps around three alpha-helices, two from one CaMBD subunit and one from the other.

• GO process: potassium ion transport (GO:0006813)
• GO component: integral component of membrane (GO:0016021)
• GO function: calcium-activated potassium channel activity (GO:0015269), calmodulin binding (GO:0005516)

There are 1789 CaMBD domains in 1786 proteins in SMART's nrdb database.

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Schumacher MA, Rivard AF, Bachinger HP, Adelman JP
• Structure of the gating domain of a Ca2+-activated K+ channel complexedwith Ca2+/calmodulin.
• Nature. 2001; 410: 1120-4

Small-conductance Ca2+-activated K+ channels (SK channels) are independentof voltage and gated solely by intracellular Ca2+. These membrane channelsare heteromeric complexes that comprise pore-forming alpha-subunits andthe Ca2+-binding protein calmodulin (CaM). CaM binds to the SK channelthrough the CaM-binding domain (CaMBD), which is located in anintracellular region of the alpha-subunit immediately carboxy-terminal tothe pore. Channel opening is triggered when Ca2+ binds the EF hands in theN-lobe of CaM. Here we report the 1.60 A crystal structure of the SKchannel CaMBD/Ca2+/CaM complex. The CaMBD forms an elongated dimer with aCaM molecule bound at each end; each CaM wraps around three alpha-helices,two from one CaMBD subunit and one from the other. As only the CaM N-lobehas bound Ca2+, the structure provides a view of both calcium-dependentand -independent CaM/protein interactions. Together with biochemical data,the structure suggests a possible gating mechanism for the SK channel.

Structure (3D structures containing this domain)

3D Structures of CaMBD domains in PDB

PDB code	Title
1g4y	1.60 A CRYSTAL STRUCTURE OF THE GATING DOMAIN FROM SMALL CONDUCTANCE POTASSIUM CHANNEL COMPLEXED WITH CALCIUM-CALMODULIN
1kkd	Solution structure of the calmodulin binding domain (CaMBD) of small conductance Ca2+-activated potassium channels (SK2)
1qx7	Crystal structure of apoCaM bound to the gating domain of small conductance Ca2+-activated potassium channel
3sjq	Crystal structure of a small conductance potassium channel splice variant complexed with calcium-calmodulin
4g27	Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance potassium channel splice variant and phenylurea
4g28	Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance potassium channel splice variant and EBIO-1
4j9y	Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance potassium channel splice variant
4j9z	Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance potassium channel splice variant and NS309
4qnh	4QNH

Links (links to other resources describing this domain)

• INTERPRO: IPR004178
• PFAM: CaMBD