Thermodynamic and molecular properties of the interaction between amphioxus calcium vector protein and its 26 kDa target.
Details
Serval ID
serval:BIB_DC4364372CA4
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Thermodynamic and molecular properties of the interaction between amphioxus calcium vector protein and its 26 kDa target.
Journal
Biochemistry
ISSN
0006-2960 (Print)
ISSN-L
0006-2960
Publication state
Published
Issued date
1995
Volume
34
Number
1
Pages
312-318
Language
english
Abstract
Calcium vector protein (CaVP) of amphioxus shares some common structural features with Ca(2+)-dependent activators such as troponin C and calmodulin, and is associated in vivo with a 26 kDa (CaVPT), a multidomain protein with one IQ- and two IgII-motifs. Isolated CaVP binds two Ca2+ ions with very different intrinsic affinity constants: K'Ca1 = 4.9 x 10(6) M-1 and K'Ca2 = 7.3 x 10(3) M-1, respectively. In the complex with CaVPT, CaVP also binds two Ca2+, but with strong positive cooperativity (nH = 1.9) and with distinctly higher affinity: K'Ca1 = 2.4 x 10(5) M-1 and K'Ca2 = 1.0 x 10(8) M-1. Since neither in the isolated CaVP nor in the complex Ca2+ binding is influenced by 2 mM MgCl2, both sites can be considered as Ca(2+)-specific. In the absence of Ca2+, the complex is stable under physiological conditions, but the interaction is governed by the principle of linked functions and Ca2+ binding to CaVP reinforces the affinity between CaVP and CaVPT 70-fold. Both proteins interact with the hydrophobic probe 2 p-toluidinylnaphthalene-6-sulfonate (TNS), but CaVPT enhances the fluorescence 45-fold, CaVP-Ca2 and metal-free CaVP only 10- and 5-fold, respectively. Complex formation between CaVPT and CaVP leads to a 3-fold reduction of the fluorescence enhancement, suggesting that a strong solvent-shielded hydrophobic core is formed. CaVP contains two highly reactional thiols (kSH > 0.3 s-1) for 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB); CaVPT contains three thiols, two of them also with kSH > 0.3 s-1 in the native state.(ABSTRACT TRUNCATED AT 250 WORDS)
Keywords
Amino Acid Sequence, Animals, Calcium/metabolism, Calcium-Binding Proteins/metabolism, Chordata, Nonvertebrate, Cysteine/analysis, Fluorescent Dyes, Models, Molecular, Molecular Sequence Data, Muscle Proteins/metabolism, Naphthalenesulfonates, Protein Binding, Protein Conformation, Sequence Homology, Amino Acid, Sulfhydryl Compounds/analysis, Thermodynamics
Pubmed
Web of science
Create date
20/12/2012 15:54
Last modification date
20/08/2019 16:01