Non-host class II ribonucleotide reductase in Thermus viruses: sequence adaptation and host interaction

PeerJ

article

Christoph Loderer¹  Karin Holmfeldt²  Daniel Lundin² 

[1] Institute for Microbiology, Technische Universität Dresden;Centre for Ecology and Evolution in Microbial model Systems—EEMiS, Linnaeus University;Department of Biochemistry and Biophysics, Stockholm University

关键词: Ribonucleotide reductase;    Horizontal gene transfer;    Bacteriophage-derived enzymes;    Thioredoxin;    Transduction;    Host-adaptation;   

DOI  :  10.7717/peerj.6700

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Ribonucleotide reductases (RNR) are essential enzymes for all known life forms. Their current taxonomic distribution suggests extensive horizontal gene transfer e.g., by processes involving viruses. To improve our understanding of the underlying processes, we characterized a monomeric class II RNR (NrdJm) enzyme from a Thermus virus, a subclass not present in any sequenced Thermus spp. genome. Phylogenetic analysis revealed a distant origin of the nrdJm gene with the most closely related sequences found in mesophiles or moderate thermophiles from the Firmicutes phylum. GC-content, codon usage and the ratio of coding to non-coding substitutions (dN/dS) suggest extensive adaptation of the gene in the virus in terms of nucleotide composition and amino acid sequence. The NrdJm enzyme is a monomeric B12-dependent RNR with nucleoside triphosphate specificity. It exhibits a temperature optimum at 60–70 °C, which is in the range of the growth optimum of Thermus spp. Experiments in combination with the Thermus thermophilus thioredoxin system show that the enzyme is able to retrieve electrons from the host NADPH pool via host thioredoxin and thioredoxin reductases. This is different from other characterized viral RNRs such as T4 phage RNR, where a viral thioredoxin is present. We hence show that the monomeric class II RNR, present in Thermus viruses, was likely transferred from an organism phylogenetically distant from the one they were isolated from, and adapted to the new host in genetic signature and amino acids sequence.

【 授权许可】

CC BY