15N NMR assignments of (Cd2+,)2-calbindin D9k and comparison with (Ca2+)2-calbindin D9k. Cadmium as a substitute for calcium in calcium-binding proteins
✍ Scribed by Mikael Akke; Sture Forsén; Walter J. Chazin
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 508 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
The amide ^15^N and ^1^H chemical shifts of (Cd^2+^)~2~‐calbindin D~9k~ are presented. A detailed comparison is made with those of (Ca^2+^)~2~‐calbindin D~9k~, showing that the (Cd^2+^)~2~ and (Ca^2+^)~2~ states of the protein are very similar, with differences predominantly located in ion‐binding loop I. The present studies were carried out on the P43G mutant calbindin D~9k~, and corroborate previous conclusions based on a comparative analysis of the ^1^H chemical shifts of the (Cd^2+^)~2~ and (Ca^2+^)~2~ states of wild‐type calbindin D~9k~. A value for the rate constant for the dissociation of cadmium from ion‐binding loop I in calbindin D~9k~ of k~off~ ≈︁ 0.6 × 10^3^ ± 0.2 × 10^3^ was estimated by analyzing line broadening in protein samples containing equal amounts of (Cd^2+^)~1~‐ and (Cd^2+^)~2~‐calbindin D~9k~.