Cation- and peptide-binding properties of human centrin 2.
Centrin and calmodulin (CaM) are closely related four-EF-hand Ca(2+)-binding proteins. While CaM is monomeric, centrin 2 is dimeric and binds only two Ca(2+) per dimer, likely to site IV in each monomer. Ca(2+) binding to centrin 2 displays pronounced negative cooperativity and a [Ca(2+)](0.5) of 30 microM. As in CaM, Ca(2+) binding leads to the exposure of a hydrophobic probe-accessible patch on the surface of centrin 2. Provided Ca(2+) is present, centrin 2 forms a 1:1 peptide:monomer complex with melittin with an affinity of 100 nM. The complex binds four instead of two Ca(2+). Our data point to surprising differences in the mode of activation of these homologous proteins.
Durussel
I
I
Department of Biochemistry, University of Geneva, Geneva, Switzerland.
Blouquit
Y
Y
Middendorp
S
S
Craescu
C T
CT
Cox
J A
JA
D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D008555:Melitten / Q000378:metabolism*; D009282:Naphthalenesulfonates / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D002135:Calcium-Binding Proteins; D002413:Cations, Divalent; D002868:Chromosomal Proteins, Non-Histone; D005456:Fluorescent Dyes; D009282:Naphthalenesulfonates; D010455:Peptides; C056608:caltractin; D008555:Melitten; C009497:2-(4-toluidino)-6-naphthalenesulfonic acid; D008274:Magnesium; D002118:Calcium