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Mol. Cells 2011; 32(6): 511-518

Published online November 9, 2011

https://doi.org/10.1007/s10059-011-0109-4

© The Korean Society for Molecular and Cellular Biology

Characterization of Novel Calmodulin Binding Domains within IQ Motifs of IQGAP1

Deok-Jin Jang1,3,*, Byungkwan Ban2,3, and Jin-A Lee2,*

1Department of Applied Biology, College of Ecology and Environment, Kyungpook National University, Daegu 742-711, Korea, 2Department of Biotechnology, College of Life Science and Nano Technology, Hannam University, Daejeon 305-811, Korea, 3These authors contributed equally to this work.

Correspondence to : *Correspondence: jangdj@knu.ac.kr (DJJ); leeja@hnu.kr (JAL)

Received: May 14, 2011; Revised: September 22, 2011; Accepted: September 22, 2011

Abstract

IQ motif-containing GTPase-activating protein 1 (IQGAP1), which is a well-known calmodulin (CaM) binding protein, is involved in a wide range of cellular processes including cell proliferation, tumorigenesis, adhesion, and migration. Interaction of IQGAP1 with CaM is important for its cellular functions. Although each IQ domain of IQGAP1 for CaM binding has been characterized in a Ca2+-dependent or -independent manner, it was not clear which IQ motifs are physiologically relevant for CaM binding in the cells. In this study, we performed immunoprecipitation using 3xFLAG-hCaM in mammalian cell lines to characterize the domains of IQGAP1 that are key for CaM binding under physiological conditions. Interestingly, using this method, we identified two novel domains, IQ(2.7-3) and IQ(3.5-4.4), within IQGAP1 that were involved in Ca2+-independent or -depen- dent CaM binding, respectively. Mutant analysis clearly showed that the hydrophobic regions within IQ(2.7-3) were mainly involved in apoCaM binding, while the basic amino acids and hydrophobic region of IQ(3.5-4.4) were required for Ca2+/CaM binding. Finally, we showed that IQ(2.7-3) was the main apoCaM binding domain and both IQ(2.7-3) and IQ(3.5-4.4) were required for Ca2+/CaM binding within IQ(1-2-3-4). Thus, we identified and characterized novel direct CaM binding motifs essential for IQGAP1. This finding indicates that IQGAP1 plays a dynamic role via direct interactions with CaM in a Ca2+-dependent or -independent manner.

Keywords calcium, calmodulin, in vitro, IQ motif, IQGAP1

Article

Research Article

Mol. Cells 2011; 32(6): 511-518

Published online December 31, 2011 https://doi.org/10.1007/s10059-011-0109-4

Copyright © The Korean Society for Molecular and Cellular Biology.

Characterization of Novel Calmodulin Binding Domains within IQ Motifs of IQGAP1

Deok-Jin Jang1,3,*, Byungkwan Ban2,3, and Jin-A Lee2,*

1Department of Applied Biology, College of Ecology and Environment, Kyungpook National University, Daegu 742-711, Korea, 2Department of Biotechnology, College of Life Science and Nano Technology, Hannam University, Daejeon 305-811, Korea, 3These authors contributed equally to this work.

Correspondence to:*Correspondence: jangdj@knu.ac.kr (DJJ); leeja@hnu.kr (JAL)

Received: May 14, 2011; Revised: September 22, 2011; Accepted: September 22, 2011

Abstract

IQ motif-containing GTPase-activating protein 1 (IQGAP1), which is a well-known calmodulin (CaM) binding protein, is involved in a wide range of cellular processes including cell proliferation, tumorigenesis, adhesion, and migration. Interaction of IQGAP1 with CaM is important for its cellular functions. Although each IQ domain of IQGAP1 for CaM binding has been characterized in a Ca2+-dependent or -independent manner, it was not clear which IQ motifs are physiologically relevant for CaM binding in the cells. In this study, we performed immunoprecipitation using 3xFLAG-hCaM in mammalian cell lines to characterize the domains of IQGAP1 that are key for CaM binding under physiological conditions. Interestingly, using this method, we identified two novel domains, IQ(2.7-3) and IQ(3.5-4.4), within IQGAP1 that were involved in Ca2+-independent or -depen- dent CaM binding, respectively. Mutant analysis clearly showed that the hydrophobic regions within IQ(2.7-3) were mainly involved in apoCaM binding, while the basic amino acids and hydrophobic region of IQ(3.5-4.4) were required for Ca2+/CaM binding. Finally, we showed that IQ(2.7-3) was the main apoCaM binding domain and both IQ(2.7-3) and IQ(3.5-4.4) were required for Ca2+/CaM binding within IQ(1-2-3-4). Thus, we identified and characterized novel direct CaM binding motifs essential for IQGAP1. This finding indicates that IQGAP1 plays a dynamic role via direct interactions with CaM in a Ca2+-dependent or -independent manner.

Keywords: calcium, calmodulin, in vitro, IQ motif, IQGAP1

Mol. Cells
Nov 30, 2023 Vol.46 No.11, pp. 655~725
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Kim et al. (pp. 710-724) demonstrated that a pathogen-derived Ralstonia pseudosolanacearum type III effector RipL delays flowering time and enhances susceptibility to bacterial infection in Arabidopsis thaliana. Shown is the RipL-expressing Arabidopsis plant, which displays general dampening of the transcriptional program during pathogen infection, grown in long-day conditions.

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