Divalent Ion-binding Properties of the Two Avian Beta-parvalbumins.
From: Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri, USA. henzlm@missouri.edu
Proteins
- Publish Date: Jan 2006
- ISSN: 1097-0134
- Volume: 62
- Issue: 1
- Pages: 270-8
- Medium: Internet
- Language: English
- Citation (JAMA): Henzl Michael T, Agah Sayeh, et al. Divalent Ion-binding Properties of the Two Avian Beta-parvalbumins.. Proteins Jan 2006;62:270-8
Abstract
Birds express three parvalbumins, one alpha isoform and two beta isoforms. The latter are known as avian thymic hormone (ATH) and avian parvalbumin 3. Although both were discovered in thymus tissue, and presumably function in T-cell maturation, they have been detected in other tissue settings. We have conducted detailed Ca2+- and Mg2+-binding studies on recombinant ATH and the C72S variant of CPV3, employing global analysis of isothermal titration calorimetry data. In Hepes-buffered saline, ATH binds Ca2+ with apparent microscopic binding constants of 2.4 +/- 0.2 x 10(8) and 1.0 +/- 0.1 x 10(8) M(-1). The corresponding values for CPV3-C72S are substantially lower, 4.5 +/- 0.5 x 10(7) and 2.4 +/- 0.2 x 10(7) M(-1), a 1.9-kcal/mol difference in binding free energy. Thus, the beta-parvalbumin lineage displays a spectrum of Ca2+-binding affinity, with ATH and the mammalian beta isoform at the high- and low-affinity extremes and CPV3 in the middle. Interestingly, despite its decreased Ca2+ affinity, CPV3-C72S exhibits increased affinity for Mg2+, relative to ATH. Whereas the latter displays Mg2+-binding constants of 2.2 +/- 0.2 x 10(4) and 1.2 +/- 0.1 x 10(4) M(-1), CPV3-C72S yields values of 5.0 +/- 0.8 x 10(4) and 2.1 +/- 0.3 x 10(4) M(-1).
Mesh Headings (Keywords): Amino Acid Sequence, Animals, Binding Sites, Birds, Calcium, Cations, Divalent, Magnesium, Models, Molecular, Molecular Sequence Data, Parvalbumins, Protein Structure, Tertiary, Rats, Sequence Alignment, Sequence Homology, Amino Acid
Check for Full Text / PubMed Unique Identifier (PMID): 16283654
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The data herein was last updated on July 8th, 2008 and may not reflect the most current and accurate data available from NLM.