Identification of a Chlorovirus PBCV-1 Protein Involved in Degrading the Host Cell Wall during Virus Infection

Authors

Irina V. Agarkova, University of Nebraska-LincolnFollow
Leslie C. Lane, University of Nebraska-LincolnFollow
David D. Dunigan, University of Nebraska-LincolnFollow
Cristian F. Quispe, University of Nebraska-LincolnFollow
Garry A. Duncan, University of Nebraska-LincolnFollow
Elad Milrot, The Weizmann Institute of ScienceFollow
Abraham Minsky, The Weizmann Institute of ScienceFollow
Ahmed Esmael, Benha UniversityFollow
Jayadri S. Ghosh, University of Nebraska-LincolnFollow
James L. Van Etten, University of Nebraska-LincolnFollow

ORCID IDs

David D. Dunigan

Garry A. Duncan

Ahmed Esmael

James L. Van Etten

Date of this Version

4-28-2021

Citation

Agarkova, I.V.; Lane, L.C.; Dunigan, D.D.; Quispe, C.F.; Duncan, G.A.; Milrot, E.; Minsky, A.; Esmael, A.; Ghosh, J.S.; Van Etten, J.L. Identification of a Chlorovirus PBCV-1 Protein Involved in Degrading the Host Cell Wall during Virus Infection. Viruses 2021, 13, 782. https://doi.org/10.3390/v13050782

Comments

CC-BY

Abstract

Chloroviruses are unusual among viruses infecting eukaryotic organisms in that they must, like bacteriophages, penetrate a rigid cell wall to initiate infection. Chlorovirus PBCV-1 infects its host, Chlorella variabilis NC64A by specifically binding to and degrading the cell wall of the host at the point of contact by a virus-packaged enzyme(s). However, PBCV-1 does not use any of the five previously characterized virus-encoded polysaccharide degrading enzymes to digest the Chlorella host cell wall during virus entry because none of the enzymes are packaged in the virion. A search for another PBCV-1-encoded and virion-associated protein identified protein A561L. The fourth domain of A561L is a 242 amino acid C-terminal domain, named A561L^D4, with cell wall degrading activity. An A561L^D4 homolog was present in all 52 genomically sequenced chloroviruses, infecting four different algal hosts. A561L^D4 degraded the cell walls of all four chlorovirus hosts, as well as several non-host Chlorella spp. Thus, A561L^D4 was not cell-type specific. Finally, we discovered that exposure of highly purified PBCV-1 virions to A561L^D4 increased the specific infectivity of PBCV-1 from about 25–30% of the particles forming plaques to almost 50%. We attribute this increase to removal of residual host receptor that attached to newly replicated viruses in the cell lysates.