Heterologous expression and functional characterization of a Truncated U ridine Kinase family protein from Arabidopsis thaliana

Abstract

Adenylate cyclases (ACs) are enzymes that convert adenine-5'-triphosphate (ATP) to cyclic 3', 5'-adenosine monophosphate (cAMP). Virtually in nature, it has been found that cAMP has an important role in chemical signaling and as a second messenger in both animals and lower eukaryotes. The second messenger systems can be synthesized and activated by enzymes for example, the cyclases that synthesize cyclic nucleotides. These small molecules bind and activate protein kinase and other proteins, thus continuing the signaling cascade. Signaling transduction occurs when an extracellular molecules activates a specific receptor located on the cell surface or inside the cell which in turn triggers a biochemical chain of events inside the cell known as signaling cascades that eventually elicits a response. This response may alter the cell's metabolism, shape, gene expression and ability to divide. Cyclic AMP can affect many different physiological and biochemical responses including the activity of protein kinases. Currently, the only annotated and experimentally confirmed ACs in higher plants are the Zea mays pollen signaling protein with a role in polarized pollen tube growth , the Arabidopsis thaliana pentatricopeptide repeat protein with a role in regulating gene expression for pathogen responses at the RNA level and bind the RNA in a sequence specific a modular fashion way, the Nicotiana benthamiana adenylyl cyclase protein responsible for the tabtoxinine-~-lactam-induced cell deaths during wildfire diseases and the Hippeastrum hybridum adenylyl cyclase protein involved in stress signalling. Otherwise not much is pre ently known about this group of molecules in higher plants as is in other organisms. Therefore, in this study, and in line with an endeavor to attempt and identify more higher plant AC candidates, we describe the cloning, partial expression and functional characterization of a putative Arabidopsis thaliana uridine kinase family protein (UKFP), which has recently been bioinformatically annotated as a possible AC but has not yet been practically tested and/or confirmed. Findings from this study have firmly confirmed that this putative candidate molecule is actually a bona fide and catalytically functional higher plant AC.