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Title: The Arabidopsis thaliana K+-uptake permease 5 (AtKUP5) contains a functional cytosolic adenylate cyclase essential for K+ transport
Authors: Al-Younis, Inas 
Wong, Aloysius 
Lemtiri-Chlieh, Fouad 
Schmöckel, Sandra 
Tester, Mark 
Gehring, Chris 
Donaldson, Lara 
Issue Date: 2018
Publisher: Frontiers Media S.A.
Source: Al-Younis, I., Wong, A., Lemtiri-Chlieh, F., Schmöckel, S., Tester, M., Gehring, C., & Donaldson, L. (2018). The Arabidopsis thaliana K+-uptake permease 5 (AtKUP5) contains a functional cytosolic adenylate cyclase essential for K+ transport. Frontiers in plant science, 9, 1645.
Journal: Frontiers in Plant Science 
Abstract: Potassium (K+) is the most abundant cation in plants, and its uptake and transport are key to growth, development and responses to the environment. Here, we report that Arabidopsis thaliana K+ uptake permease 5 (AtKUP5) contains an adenylate cyclase (AC) catalytic center embedded in its N-terminal cytosolic domain. The purified recombinant AC domain generates cAMP in vitro; and when expressed in Escherichia coli, increases cAMP levels in vivo. Both the AC domain and full length AtKUP5 rescue an AC-deficient E. coli mutant, cyaA, and together these data provide evidence that AtKUP5 functions as an AC. Furthermore, full length AtKUP5 complements the Saccharomyces cerevisiae K+ transport impaired mutant, trk1 trk2, demonstrating its function as a K+ transporter. Surprisingly, a point mutation in the AC center that impairs AC activity, also abolishes complementation of trk1 trk2, suggesting that a functional catalytic AC domain is essential for K+ uptake. AtKUP5-mediated K+ uptake is not affected by cAMP, the catalytic product of the AC, but, interestingly, causes cytosolic cAMP accumulation. These findings are consistent with a role for AtKUP5 as K+ flux sensor, where the flux-dependent cAMP increases modulate downstream components essential for K+ homeostasis, such as cyclic nucleotide gated channels.
DOI: 10.3389/fpls.2018.01645
Appears in Collections:Scholarly Publications

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