Estonian Biocentre, Tartu, Estonia.
Bioessays. 2011 Aug;33(8):626-35. doi: 10.1002/bies.201000126. Epub 2011 Jun 1.
A crucially important part of the biosphere - the virosphere - is too often overlooked. Inclusion of the virosphere into the global picture of protein structure space reveals that 63 protein domain superfamilies in viruses do not have any structural and evolutionary relatives in modern cellular organisms. More than half of these have functions which are not virus-specific and thus might be a source of new folds and functions for cellular life. The number of viruses on the planet exceeds that of cells by an order of magnitude and viruses evolve up to six orders of magnitude faster. As a result, cellular species are subject to a constitutive 'flow-through' of new viral genetic material. Due to this and the relaxed evolutionary constraints in viruses, the transfer of domains between host-to-virus could be a mechanism for accelerated protein evolution. The virosphere could be an engine for the genesis of protein structures, and may even have been so before the last universal common ancestor of cellular life.
生物圈中一个至关重要的部分——病毒圈——经常被忽视。将病毒圈纳入全球蛋白质结构空间图景中，可以发现病毒中有 63 个蛋白结构域超家族在现代细胞生物中没有任何结构和进化上的亲缘关系。其中一半以上的功能并非病毒所特有，因此可能成为细胞生命中新结构和功能的来源。地球上的病毒数量超过细胞数量的一个数量级，病毒的进化速度比细胞快六个数量级。因此，细胞物种不断受到新的病毒遗传物质的“流动”影响。由于这一点，以及病毒中相对宽松的进化限制，宿主与病毒之间的结构域转移可能是加速蛋白质进化的一种机制。病毒圈可能是蛋白质结构起源的引擎，甚至可能在细胞生命的最后一个共同祖先出现之前就是如此。
