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Phycodnavirus potassium ion channel proteins question the virus molecular piracy hypothesis.

Hamacher K, Greiner T, Ogata H, Van Etten JL, Gebhardt M, Villarreal LP, Cosentino C, Moroni A, Thiel G - PLoS ONE (2012)

Bottom Line: To determine if these viral K(+) channels are the product of molecular piracy from their hosts, we compared the sequences of the K(+) channel pore modules from seven phycodnaviruses to the K(+) channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced.However, the bacterial protein lacks the consensus motif of all K(+) channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium.Alternatively the viral proteins could be the origin of K(+) channels in algae and perhaps even all cellular organisms.

View Article: PubMed Central - PubMed

Affiliation: Computational Biology Group, Technische Universit├Ąt Darmstadt, Darmstadt, Germany.

ABSTRACT
Phycodnaviruses are large dsDNA, algal-infecting viruses that encode many genes with homologs in prokaryotes and eukaryotes. Among the viral gene products are the smallest proteins known to form functional K(+) channels. To determine if these viral K(+) channels are the product of molecular piracy from their hosts, we compared the sequences of the K(+) channel pore modules from seven phycodnaviruses to the K(+) channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced. C. variabilis is the host for two of the viruses PBCV-1 and NY-2A and E. siliculosus is the host for the virus EsV-1. Systematic phylogenetic analyses consistently indicate that the viral K(+) channels are not related to any lineage of the host channel homologs and that they are more closely related to each other than to their host homologs. A consensus sequence of the viral channels resembles a protein of unknown function from a proteobacterium. However, the bacterial protein lacks the consensus motif of all K(+) channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium. Collectively, our results indicate that the viruses did not acquire their K(+) channel-encoding genes from their current algal hosts by gene transfer; thus alternative explanations are required. One possibility is that the viral genes arose from ancient organisms, which served as their hosts before the viruses developed their current host specificity. Alternatively the viral proteins could be the origin of K(+) channels in algae and perhaps even all cellular organisms.

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Multiple sequence alignment of pore modules of K+ channel proteins from E. siliculosus.The pore-forming unit begins with the transmembrane domain, prior to the selectivity filter and it finishes at the end of the transmembrane domain after the filter. The selectivity filter sequence is in black; aromatic amino acids upstream of the filter are marked in grey; the transmembrane domains are underlined.
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pone-0038826-g004: Multiple sequence alignment of pore modules of K+ channel proteins from E. siliculosus.The pore-forming unit begins with the transmembrane domain, prior to the selectivity filter and it finishes at the end of the transmembrane domain after the filter. The selectivity filter sequence is in black; aromatic amino acids upstream of the filter are marked in grey; the transmembrane domains are underlined.

Mentions: We restricted our phylogenetic analyses to the pore module of these proteins, which comprises two transmembrane domains, a pore helix and the canonical selectivity filter sequence [4]. To identify the pore modules of the putative host channel proteins, all amino acid sequences were subjected to bioinformatics methods for transmembrane domain prediction (see Materials and Methods). A consensus of the predictions for the pore modules from C. variabilis and E. siliculosus are shown in Fig. 3 and Fig. 4, respectively. Several two-pore K+-channels were identified in E. siliculosus. Each pore is listed individually and the pores are indexed as x.1 or x.2 for the N- and C-terminal pores, respectively.


Phycodnavirus potassium ion channel proteins question the virus molecular piracy hypothesis.

Hamacher K, Greiner T, Ogata H, Van Etten JL, Gebhardt M, Villarreal LP, Cosentino C, Moroni A, Thiel G - PLoS ONE (2012)

Multiple sequence alignment of pore modules of K+ channel proteins from E. siliculosus.The pore-forming unit begins with the transmembrane domain, prior to the selectivity filter and it finishes at the end of the transmembrane domain after the filter. The selectivity filter sequence is in black; aromatic amino acids upstream of the filter are marked in grey; the transmembrane domains are underlined.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369850&req=5

pone-0038826-g004: Multiple sequence alignment of pore modules of K+ channel proteins from E. siliculosus.The pore-forming unit begins with the transmembrane domain, prior to the selectivity filter and it finishes at the end of the transmembrane domain after the filter. The selectivity filter sequence is in black; aromatic amino acids upstream of the filter are marked in grey; the transmembrane domains are underlined.
Mentions: We restricted our phylogenetic analyses to the pore module of these proteins, which comprises two transmembrane domains, a pore helix and the canonical selectivity filter sequence [4]. To identify the pore modules of the putative host channel proteins, all amino acid sequences were subjected to bioinformatics methods for transmembrane domain prediction (see Materials and Methods). A consensus of the predictions for the pore modules from C. variabilis and E. siliculosus are shown in Fig. 3 and Fig. 4, respectively. Several two-pore K+-channels were identified in E. siliculosus. Each pore is listed individually and the pores are indexed as x.1 or x.2 for the N- and C-terminal pores, respectively.

Bottom Line: To determine if these viral K(+) channels are the product of molecular piracy from their hosts, we compared the sequences of the K(+) channel pore modules from seven phycodnaviruses to the K(+) channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced.However, the bacterial protein lacks the consensus motif of all K(+) channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium.Alternatively the viral proteins could be the origin of K(+) channels in algae and perhaps even all cellular organisms.

View Article: PubMed Central - PubMed

Affiliation: Computational Biology Group, Technische Universit├Ąt Darmstadt, Darmstadt, Germany.

ABSTRACT
Phycodnaviruses are large dsDNA, algal-infecting viruses that encode many genes with homologs in prokaryotes and eukaryotes. Among the viral gene products are the smallest proteins known to form functional K(+) channels. To determine if these viral K(+) channels are the product of molecular piracy from their hosts, we compared the sequences of the K(+) channel pore modules from seven phycodnaviruses to the K(+) channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced. C. variabilis is the host for two of the viruses PBCV-1 and NY-2A and E. siliculosus is the host for the virus EsV-1. Systematic phylogenetic analyses consistently indicate that the viral K(+) channels are not related to any lineage of the host channel homologs and that they are more closely related to each other than to their host homologs. A consensus sequence of the viral channels resembles a protein of unknown function from a proteobacterium. However, the bacterial protein lacks the consensus motif of all K(+) channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium. Collectively, our results indicate that the viruses did not acquire their K(+) channel-encoding genes from their current algal hosts by gene transfer; thus alternative explanations are required. One possibility is that the viral genes arose from ancient organisms, which served as their hosts before the viruses developed their current host specificity. Alternatively the viral proteins could be the origin of K(+) channels in algae and perhaps even all cellular organisms.

Show MeSH
Related in: MedlinePlus