Mutational Analysis of a Red Fluorescent Protein-Based Calcium Ion Indicator

Sensors

Haley J. Carlson¹ 

[1] Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada; E-Mail

关键词: red fluorescent protein;    calcium ion;    genetically encoded sensor;    mutagenesis;    spectroscopy;   

DOI  :  10.3390/s130911507

来源: mdpi

【 摘 要 】

As part of an ongoing effort to develop genetically encoded calcium ion (Ca²⁺) indicators we recently described a new variant, designated CH-GECO2.1, that is a genetic chimera of the red fluorescent protein (FP) mCherry, calmodulin (CaM), and a peptide that binds to Ca²⁺-bound CaM. In contrast to the closely related Ca²⁺ indicator R-GECO1, CH-GECO2.1 is characterized by a much higher affinity for Ca²⁺ and a sensing mechanism that does not involve direct modulation of the chromophore pK_a. To probe the structural basis underlying the differences between CH-GECO2.1 and R-GECO1, and to gain a better understanding of the mechanism of CH-GECO2.1, we have constructed, purified, and characterized a large number of variants with strategic amino acid substitutions. This effort led us to identify Gln163 as the key residue involved in the conformational change that transduces the Ca²⁺ binding event into a change in the chromophore environment. In addition, we demonstrate that many of the substitutions that differentiate CH-GECO2.1 and R-GECO1 have little influence on both the K_d for Ca²⁺ and the sensing mechanism, and that the interdomain linkers and interfaces play important roles.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.