NDLI: The solution structures of two soybean calmodulin isoforms provide a structural basis for their selective target activation properties.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Ishida, Hiroaki Huang, Hao Yamniuk, Aaron P. Takaya, Yoshiaki Vogel, Hans J.
Description	Author Affiliation: Ishida H ( Structural Biology Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.)
Abstract	The intracellular calcium ion is one of the most important secondary messengers in eukaryotic cells. Ca(2+) signals are translated into physiological responses by EF-hand calcium-binding proteins such as calmodulin (CaM). Multiple CaM isoforms occur in plant cells, whereas only a single CaM protein is found in animals. Soybean CaM isoform 1 (sCaM1) shares 90% amino acid sequence identity with animal CaM (aCaM), whereas sCaM4 is only 78% identical. These two sCaM isoforms have distinct target-enzyme activation properties and physiological functions. sCaM4 is highly expressed during the self-defense reaction of the plant and activates the enzyme nitric-oxide synthase (NOS), whereas sCaM1 is incapable of activating NOS. The mechanism of selective target activation by plant CaM isoforms is poorly understood. We have determined high resolution NMR solution structures of Ca(2+)-sCaM1 and -sCaM4. These were compared with previously determined Ca(2+)-aCaM structures. For the N-lobe of the protein, the solution structures of Ca(2+)-sCaM1, -sCaM4, and -aCaM all closely resemble each other. However, despite the high sequence identity with aCaM, the C-lobe of Ca(2+)-sCaM1 has a more open conformation and consequently a larger hydrophobic target-protein binding pocket than Ca(2+)-aCaM or -sCaM4, the presence of which was further confirmed through biophysical measurements. The single Val-144 --> Met substitution in the C-lobe of Ca(2+)-sCaM1, which restores its ability to activate NOS, alters the structure of the C-lobe to a more closed conformation resembling Ca(2+)-aCaM and -sCaM4. The relationships between the structural differences in the two Ca(2+)-sCaM isoforms and their selective target activation properties are discussed.
ISSN	00219258
e-ISSN	1083351X
Journal	Journal of Biological Chemistry
Issue Number	21
Volume Number	283
Language	English
Publisher	American Society for Biochemistry and Molecular Biology (United States)
Publisher Date	2008-05-23
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Calmodulin Chemistry Metabolism Soybeans Amino Acid Sequence Genetics Calorimetry Hydrophobic And Hydrophilic Interactions Models, Molecular Molecular Sequence Data Nuclear Magnetic Resonance, Biomolecular Protein Isoforms Protein Structure, Tertiary Sequence Alignment Sequence Homology, Amino Acid Surface Properties Research Support, Non-U.S. Gov't Biochemistry Molecular Biology
Content Type	Text
Resource Type	Article
Subject	Cell Biology Biochemistry Molecular Biology

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