Researcher provided data to show that Ca2 binds to the BK ch

Researcher provided data to show that Ca2+ binds to the BK channel at 2 specific sites. At present, there is more evidence to suggest that there are actually 2 calcium binding sites on the channel. What data support this idea?

Solution

Answer:

Evidences which suggest that there are actually 2 calcium binding sites on the BK channel are:

1. Domain-swapping experiments across species revealed that the Ca²⁺-sensing properties of the BK_Ca channel segregate with the channel\'s cytoplasmic domain, not its integral membrane domain, and that there is an acidic region in this cytoplasmic domain where mutations alter Ca²⁺ sensing.

This 28-amino acid region was called the “Ca²⁺ bowl” and was proposed to form a Ca²⁺-binding site.

2. Electrophysiological and crystallographic analysis revealed that two physically distinct Ca²⁺-binding sites on the RCK domain are structurally and energetically coupled to one another, and further define a key interaction that mediates this allosteric coupling to tune Ca²⁺ sensitivity of the channel.