Phylogenetic analysis and detections of selective pressure on the CVNH domains
CVNH 结构域进化分析及选择压力检测

Cyanovirin-N (CV-N) is a novel protein with broad-spectrum antiviral activity. Its homologs constitute a protein family named CVNH (Cyanovirin-N homology), all possessing the evolutionarily conserved anti-HIV (Human immunodeficiency virus) domain. In this research, more details about the patchy organism distribution of CVNH domain have been revealed by reconstructing gene trees. And duplicated CVNH sequences have also been identified in a wide range of species including Aspergillus niger, Neosartorya fischeri NRRL 181, Penicillium chrysogenum Wisconsin 54-1255, Neurospora crassa, Cyanothece sp. PCC and Ceratopteris richardii. Besides these findings, both the mechanistic and mechanistic-empirical combination (MEC) models were used to analyze the adaptive evolution of amino acid sites in the CVNH domain. Our results showed that: (i) neither model reveals significant sites undergoing positive selection; (ii) purifying selection has played a dominant role during CVNH evolution; and (iii) the MEC model better fits the CVNH data set. Furthermore, the ancestral branch leading to Cyanothece sp. PCC 7822 and 7424 were examined by using “branch-specific” and “branch-site” models. Six positively selected sites (34L, 63L, 13H, 76C, 78K and 80I) were identified on the branch. This research provides a basis for future functional test of CVNHs as well as enhancing their antiviral activity through genetic modification.