Structure of the N-terminal calcium sensor domain of centrin reveals the biochemical basis for domain-specific function.
Centrin is an essential component of microtubule-organizing centers in organisms ranging from algae and yeast to humans. It is an EF-hand calcium-binding protein with homology to calmodulin but distinct calcium binding properties. In a previously proposed model, the C-terminal domain of centrin serves as a constitutive anchor to target proteins, and the N-terminal domain serves as the sensor of calcium signals. The three-dimensional structure of the N-terminal domain of Chlamydomonas rheinhardtii centrin has been determined in the presence of calcium by solution NMR spectroscopy. The domain is found to occupy an open conformation typical of EF-hand calcium sensors. Comparison of the N- and C-terminal domains of centrin reveals a structural and biochemical basis for the domain specificity of interactions with its cellular targets and the distinct nature of centrin relative to other EF-hand proteins. An NMR titration of the centrin N-terminal domain with a fragment of the known centrin target Sfi1 reveals binding of the peptide to a discrete site on the protein, which supports the proposal that the N-terminal domain serves as a calcium sensor in centrin.
Sheehan
Jonathan H
JH
Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232-8725, USA.
Bunick
Christopher G
CG
Hu
Haitao
H
Fagan
Patricia A
PA
Meyn
Susan M
SM
Chazin
Walter J
WJ
D000818:Animals; D001665:Binding Sites; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000502:physiology; D020832:EF Hand Motifs; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D012996:Solutions; D017186:Titrimetry
D002135:Calcium-Binding Proteins; D002868:Chromosomal Proteins, Non-Histone; D012996:Solutions; C056608:caltractin