Comparative analysis of K+-channels from two Chlorella species: information on their role in endosymbiosis and on the origin of viral K+-channels

目前，两种小球藻的基因组已经完全测序。申请者是一个国际项目的一部分，该项目涉及到他们的比较分析。其中一种是普通小球藻，是一种典型的自由生物；另一种是草履虫的内生共生体，与前者不同的是，NC64A也是小球藻病毒的宿主。目的是确定两个小球藻基因组中的K+通道。这将回答一个问题，即在许多小球藻病毒中发现的微型K+通道基因是否是从宿主那里盗用分子的结果。这对于了解病毒和宿主之间的基因流动方向是一个重要的问题。比较分析和表达研究将进一步回答内共生和自由生活方式是否需要具有不同功能特性的K+-通道的问题。对这两个基因组的筛选已经发现了具有不寻常结构的类似K+通道的序列；例如，其中一个具有K+通道的特征，但不携带部分K+通道特征序列。对这些不寻常的通道蛋白的克隆和结构/功能分析将揭示关于K+通道的不同结构的有趣信息。

Currently the genomes of two Chlorella species are fully sequenced. The applicant is part of an international project, which is involved in their comparative analysis. One species, Cholrella vulgaris, is a typical free living organism, while the other one, C. NC64A, is a endosymbiont of Paramecium bursaria; unlike the former C. NC64A is also a host for Chlorella viruses. The goal is to identify the K+-channels in the two Chlorella genomes. This will answer the question whether or not the miniature K+-channel genes found in many Chlorella viruses are the result of molecular piracy from their host. This is an important issue for understanding the direction of gene fluxes between viruses and hosts. A comparative analysis together with expression studies will further answer the question whether or not K+-channels with different functional properties are required for the endosymbiotic versus the free style of living. Screening of the two genomes has already uncovered K+-channel like sequences with unusual structures; one for example has the hallmarks of a K+-channel but does not carry parts of the K+-channel signature sequence. Cloning and structure/ function analysis of these unusual channel proteins will uncover interesting information on alternative architectures of K+-channels.