Functional Crypto-Adenylate Cyclases Operate in Complex Plant Proteins

Inas Al-Younis; Basem Moosa; Mateusz Kwiatkowski; Krzysztof Jaworski; Aloysius Wong; Chris Gehring

doi:10.3389/fpls.2021.711749

Functional Crypto-Adenylate Cyclases Operate in Complex Plant Proteins

Front Plant Sci. 2021 Aug 12:12:711749. doi: 10.3389/fpls.2021.711749. eCollection 2021.

Authors

Inas Al-Younis¹, Basem Moosa², Mateusz Kwiatkowski³, Krzysztof Jaworski³, Aloysius Wong^{4

5}, Chris Gehring^{1

6}

Affiliations

¹ Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
² Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
³ Chair of Plant Physiology and Biotechnology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University in Toruń, Toruń, Poland.
⁴ Department of Biology, College of Science and Technology, Wenzhou-Kean University, Wenzhou, China.
⁵ Zhejiang Bioinformatics International Science and Technology Cooperation Center of Wenzhou-Kean University, Wenzhou, China.
⁶ Department of Chemistry, Biology & Biotechnology, University of Perugia, Perugia, Italy.

Abstract

Adenylyl cyclases (ACs) and their catalytic product cAMP are regulatory components of many plant responses. Here, we show that an amino acid search motif based on annotated adenylate cyclases (ACs) identifies 12 unique Arabidopsis thaliana candidate ACs, four of which have a role in the biosynthesis of the stress hormone abscisic acid (ABA). One of these, the 9-cis-epoxycarotenoid dioxygenase (NCED3 and At3g14440), was identified by sequence and structural analysis as a putative AC and then tested experimentally with two different methods. Given that the in vitro activity is low (fmoles cAMP pmol^-1 protein min^-1), but highly reproducible, we term the enzyme a crypto-AC. Our results are consistent with a role for ACs with low activities in multi-domain moonlighting proteins that have at least one other distinct molecular function, such as catalysis or ion channel activation. We propose that crypto-ACs be examined from the perspective that considers their low activities as an innate feature of regulatory ACs embedded within multi-domain moonlighting proteins. It is therefore conceivable that crypto-ACs form integral components of complex plant proteins participating in intra-molecular regulatory mechanisms, and in this case, potentially linking cAMP to ABA synthesis.

Keywords: 3',5'-cyclic adenosine monophosphate; 9-cis-epoxycarotenoid 11,12 dioxygenase; Arabidopsis thaliana; adenylyl cyclase; catalytic center; crypto-enzymes; multi-domain moonlighting enzymes.