Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, P O Box 218, Hawthorn, VIC, 3122, Australia.
Plant Mol Biol. 2011 Mar;75(4-5):413-30. doi: 10.1007/s11103-011-9737-5. Epub 2011 Feb 10.
Research in recent years on plant Major Intrinsic Proteins (MIPs), commonly referred to as 'aquaporins', has seen a vast expansion in the substrates found to be transported via these membrane channels. The diversity in sizes, chemical nature and physiological significance of these substrates has meant a need to critically analyse the possible structural and biochemical properties of MIPs that transport these, in order to understand their roles. In this work we have undertaken a comprehensive analysis of all plant MIPs, coming from different families, that have been proven to transport ammonia, boron, carbon dioxide, hydrogen peroxide, silicon and urea. The sequences were analysed for all primary selectivity-related motifs (NPA motifs, ar/R filter, P1-P5 residues). In addition, the putative regulatory phosphorylation and glycosylation sites and mechanistic regulators such as loop lengths have been analysed. Further, nine specificity-determining positions (SDPs) were predicted for each group. The results show the ar/R filter residues, P2-P4 positions and some of the SDPs are characteristic for certain groups, and O-glycosylation sites are unique to a subgroup while N-glycosylation was characteristic of the other MIPs. Certain residues, especially in loop C, and structural parameters such as loop lengths also contribute to the uniqueness of groups. The comprehensive analysis makes significant inroads into appraising the intriguing diversity of plant MIPs and their roles in fundamental life processes, and provides tools for plant selections, protein engineering and transgenics.
近年来，对植物主要内在蛋白（MIPs）的研究，通常被称为“水通道蛋白”，在通过这些膜通道运输的底物方面有了巨大的扩展。这些底物的大小、化学性质和生理意义的多样性意味着需要对运输这些底物的 MIPs 的可能结构和生化特性进行批判性分析，以了解它们的作用。在这项工作中，我们对所有已被证明能运输氨、硼、二氧化碳、过氧化氢、硅和尿素的不同家族的植物 MIPs 进行了全面分析。对所有与选择性相关的主要基序（NPA 基序、ar/R 过滤器、P1-P5 残基）进行了序列分析。此外，还分析了推测的调节磷酸化和糖基化位点以及环长度等机械调节剂。此外，还预测了每组中的九个特异性决定位置（SDP）。结果表明，ar/R 过滤器残基、P2-P4 位置和一些 SDP 是某些组的特征，O-糖基化位点是特定亚组所特有的，而 N-糖基化是其他 MIPs 的特征。某些残基，特别是环 C 中的残基，以及结构参数，如环长度，也有助于组的独特性。全面分析为评估植物 MIPs 的迷人多样性及其在基本生命过程中的作用提供了重要的依据，并为植物选择、蛋白质工程和转基因提供了工具。
