Calbindin D28K is a six-EF-hand calcium-binding protein found in the brain, peripheral nervous system, kidney, and intestine. There is a paucity of information on the effects of calcium binding on calbindin D28K structure. To further examine the mechanism and structural consequences of calcium binding to calbindin D28K we performed detailed complementary heteronuclear NMR and microelectrospray mass spectrometry investigations of the calcium-induced conformational changes of calbindin D28K. The combined use of these two powerful analytical techniques clearly and very rapidly demonstrates the following: (i) apo-calbindin D28K has an ordered structure which changes to a notably different ordered conformation upon Ca2+ loading, (ii) calcium binding is a sequential process and not a simultaneous event, and (iii) EF-hands 1, 3, 4, and 5 take up Ca2+, whereas EF-hands 2 and 6 do not. Our results support the opinion that calbindin D28K has characteristics of both a calcium sensor and a buffer.
- Calbindin D
- Conformational response to calcium binding
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology