Structural and Dynamic Characterization of a Neuron-Specific Protein Kinase C Substrate, Neurogranin
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- 作者：Xiaoyuan Ran ; Hong-Hua Miao ; Fwu-Shan Sheu ; and Daiwen Yang
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：May 6, 2003
- 年：2003
- 卷：42
- 期：17
- 页码：5143 - 5150
- 全文大小：126K
- 年卷期：v.42,no.17(May 6, 2003)
- ISSN：1520-4995
文摘
Neurogranin/RC3 is a neuron-specific, Ca2+-sensitive calmodulin binding protein and a specificprotein kinase C substrate. Neurogranin may function to regulate calmodulin levels at specific sites inneurons through phosphorylation at serine residue within its IQ motif, oxidation outside the IQ motif, orchanges in local cellular Ca2+ concentration. To gain insight into the functional role of neurogranin in theregulation of calmodulin-dependent activities, we investigated the structure and dynamics of a full-lengthrat neurogranin protein with 78 amino acids using triple resonance NMR techniques. In the absence ofcalmodulin or PKC, neurogranin exists in an unfolded form as evidenced by high backbone mobility andthe absence of long-range nuclear Overhauser effect (NOE). Analyses of the chemical shifts 13C
, 13C
,and 1H reveal the presence of a local -helical structure for the region between residues G25-A42.Three-bond 1HN-1H coupling constants support the finding that the sequence between residues G25 andA42 populates a non-native helical structure in the unfolded neurogranin. Homonuclear NOE results areconsistent with the conclusions drawn from chemical shifts and coupling constants. 15N relaxation dataindicate motional restrictions on a nanosecond time scale in the region from D15 to S48. Spectral densitiesand order parameters data further confirm that the unfolded neurogranin exists in conformation with residualsecondary structures. The medium mobility of the nascent helical region may help to reduce the entropyloss when neurogranin binds to its targets, but the complex between neurogranin and calmodulin is notstable enough for structural determination by NMR. Calmodulin titration of neurogranin indicates thatresidues D15-G52 of neurogranin undergo significant structural changes upon binding to calmodulin.
, 13C,and 1H reveal the presence of a local -helical structure for the region between residues G25-A42.Three-bond 1HN-1H coupling constants support the finding that the sequence between residues G25 andA42 populates a non-native helical structure in the unfolded neurogranin. Homonuclear NOE results areconsistent with the conclusions drawn from chemical shifts and coupling constants. 15N relaxation dataindicate motional restrictions on a nanosecond time scale in the region from D15 to S48. Spectral densitiesand order parameters data further confirm that the unfolded neurogranin exists in conformation with residualsecondary structures. The medium mobility of the nascent helical region may help to reduce the entropyloss when neurogranin binds to its targets, but the complex between neurogranin and calmodulin is notstable enough for structural determination by NMR. Calmodulin titration of neurogranin indicates thatresidues D15-G52 of neurogranin undergo significant structural changes upon binding to calmodulin.