A functional calcium-transporting ATPase encoded by chlorella viruses.
Calcium-transporting ATPases (Ca(2+) pumps) are major players in maintaining calcium homeostasis in the cell and have been detected in all cellular organisms. Here, we report the identification of two putative Ca(2+) pumps, M535L and C785L, encoded by chlorella viruses MT325 and AR158, respectively, and the functional characterization of M535L. Phylogenetic and sequence analyses place the viral proteins in group IIB of P-type ATPases even though they lack a typical feature of this class, a calmodulin-binding domain. A Ca(2+) pump gene is present in 45 of 47 viruses tested and is transcribed during virus infection. Complementation analysis of the triple yeast mutant K616 confirmed that M535L transports calcium ions and, unusually for group IIB pumps, also manganese ions. In vitro assays show basal ATPase activity. This activity is inhibited by vanadate, but, unlike that of other Ca(2+) pumps, is not significantly stimulated by either calcium or manganese. The enzyme forms a (32)P-phosphorylated intermediate, which is inhibited by vanadate and not stimulated by the transported substrate Ca(2+), thus confirming the peculiar properties of this viral pump. To our knowledge this is the first report of a functional P-type Ca(2+)-transporting ATPase encoded by a virus.
Bonza
Maria Cristina
MC
Dipartimento di Biologia e Istituto di Biofisica del CNR, Università degli Studi di Milano, Milano, Italy.
Martin
Holger
H
Kang
Ming
M
Lewis
Gentry
G
Greiner
Timo
T
Giacometti
Sonia
S
Van Etten
James L
JL
De Michelis
Maria Ida
MI
Thiel
Gerhard
G
Moroni
Anna
A
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002708:Chlorella / Q000821:virology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008345:Manganese / Q000378:metabolism; D008969:Molecular Sequence Data; D017862:Phycodnaviridae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014638:Vanadates / Q000494:pharmacology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics
D004791:Enzyme Inhibitors; D014764:Viral Proteins; D014638:Vanadates; D008345:Manganese; D000251:Adenosine Triphosphatases; D002118:Calcium