Calmodulin binding domain
{{Short description|Protein domain}}
{{Infobox protein family
| Symbol = CaMBD
| Name = CaMBD
| image = PDB 1kkd EBI.jpg
| width =
| caption = solution structure of the calmodulin binding domain (cambd) of small conductanceCa2+-activated potassium channels (sk2)
| Pfam = PF02888
| Pfam_clan =
| InterPro = IPR004178
| SMART =
| PROSITE =
| MEROPS =
| SCOP = 1kkd
| TCDB =
| OPM family =
| OPM protein =
| CAZy =
| CDD =
}}
In molecular biology, calmodulin binding domain (CaMBD) is a protein domain found in small-conductance calcium-activated potassium channels (SK channels). These channels are independent of voltage and gated solely by intracellular Ca2+. They are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM).{{cite journal |vauthors=Schumacher MA, Rivard AF, Bachinger HP, Adelman JP | title = Structure of the gating domain of a Ca2+-activated K+ channel complexed with Ca2+/calmodulin | journal = Nature | volume = 410 | issue = 6832 | pages = 1120–4 |date=April 2001 | pmid = 11323678 | doi = 10.1038/35074145 | bibcode = 2001Natur.410.1120S | s2cid = 205016620 }} CaM binds to the SK channel through the 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. 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.