Single amino acid alteration between valine and isoleucine determines the distinct pyrabactin selectivity by PYL1 and PYL2. Author Xiaoqiu Yuan, Ping Yin, Qi Hao, Chuangye Yan, Jiawei Wang, Nieng Yan Publication Year 2010 Type Journal Article Abstract Abscisic acid (ABA) is one of the most important phytohormones in plant. PYL proteins were identified to be ABA receptors in Arabidopsis thaliana. Despite the remarkably high degree of sequence similarity, PYL1 and PYL2 exhibit distinct responses toward pyrabactin, an ABA agonist. PYL1 inhibits protein phosphatase type 2C upon binding of pyrabactin. In contrast, PYL2 appears relatively insensitive to this compound. The crystal structure of pyrabactin-bound PYL1 revealed that most of the PYL1 residues involved in pyrabactin binding are conserved, hence failing to explain the selectivity of pyrabactin for PYL1 over PYL2. To understand the molecular basis of pyrabactin selectivity, we determined the crystal structure of PYL2 in complex with pyrabactin at 1.64 A resolution. Structural comparison and biochemical analyses demonstrated that one single amino acid alteration between a corresponding valine and isoleucine determines the distinct pyrabactin selectivity by PYL1 and PYL2. These characterizations provide an important clue to dissecting the redundancy of PYL proteins. Keywords Protein Structure, Tertiary, Crystallography, X-Ray, Receptors, Cell Surface, Arabidopsis, Arabidopsis Proteins, Abscisic Acid, Isoleucine, Valine Journal J Biol Chem Volume 285 Issue 37 Pages 28953-8 Date Published 2010 Sep 10 ISSN Number 1083-351X DOI 10.1074/jbc.M110.160192 Alternate Journal J Biol Chem PMCID PMC2937922 PMID 20630864 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML