A Functional K+ Channel from Tetraselmis Virus 1, a Member of the Mimiviridae

Authors

Kerri Kukovetz, Technische Universität DarmstadtFollow
Brigitte Hertel, Technische Universität DarmstadtFollow
Christopher R. Schvarcz, University of Hawaii at ManoaFollow
Andrea Saponaro, Università degli Studi di MilanoFollow
Mirja Manthey, Technische Universität DarmstadtFollow
Ulrike Burk, Technische Universität DarmstadtFollow
Timo Greiner, Brandenburg Medical SchoolFollow
Grieg F. Steward, University of Hawaii at ManoaFollow
James L. Van Etten, University of Nebraska-LincolnFollow
Anna Moroni, Università degli Studi di MilanoFollow
Gerhard Thiel, Technische Universität Darmstadt, GermanyFollow
Oliver Rauh, Technische UniversitatFollow

ORCID IDs

Christopher R. Schvarcz https://orcid.org/0000-0003-3789-2033

Andrea Saponaro https://orcid.org/0000-0001-5035-5174

Timo Greiner https://orcid.org/0000-0002-0909-570X

James L. Van Etten https://orcid.org/0000-0002-5063-0049

Anna Moroni https://orcid.org/0000-0002-1860-406X

Gerhard Thiel https://orcid.org/0000-0002-2335-1351

Oliver Rauh https://orcid.org/0000-0003-1082-8656

Document Type

Article

Date of this Version

9-29-2020

Citation

Viruses 2020, 12, 1107; doi:10.3390/v12101107

Comments

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license

Abstract

Potassium ion (K+) channels have been observed in diverse viruses that infect eukaryotic marine and freshwater algae. However, experimental evidence for functional K+ channels among these alga-infecting viruses has thus far been restricted to members of the family Phycodnaviridae, which are large, double-stranded DNA viruses within the phylum Nucleocytoviricota. Recent sequencing projects revealed that alga-infecting members of Mimiviridae, another family within this phylum, may also contain genes encoding K+ channels. Here we examine the structural features and the functional properties of putative K+ channels from four cultivated members of Mimiviridae. While all four proteins contain variations of the conserved selectivity filter sequence of K+ channels, structural prediction algorithms suggest that only two of them have the required number and position of two transmembrane domains that are present in all K+ channels. After in vitro translation and reconstitution of the four proteins in planar lipid bilayers, we confirmed that one of them, a 79 amino acid protein from the virus Tetraselmis virus 1 (TetV-1), forms a functional ion channel with a distinct selectivity for K+ over Na+ and a sensitivity to Ba²⁺. Thus, virus-encoded K+ channels are not limited to Phycodnaviridae but also occur in the members of Mimiviridae. The large sequence diversity among the viral K+ channels implies multiple events of lateral gene transfer.