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Origin and Evolution of GALA-LRR, a New Member of the CC-LRR Subfamily: From Plants to Bacteria?

Summary: Origin and Evolution of GALA-LRR, a New Member of the
CC-LRR Subfamily: From Plants to Bacteria?
Andrey V. Kajava1
*, Maria Anisimova2,3
, Nemo Peeters4
1 Centre de Recherches de Biochimie Macromole´culaire, CNRS, University of Montpellier 1 and 2, Montpellier, France, 2 Institute of Computational Science, ETH Zurich,
Zurich, Switzerland, 3 Swiss Institute of Bioinformatics, Lausanne, Switzerland, 4 Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441-2594 (INRA-CNRS),
Castanet-Tolosan, France
The phytopathogenic bacterium Ralstonia solanacearum encodes type III effectors, called GALA proteins, which contain F-
box and LRR domains. The GALA LRRs do not perfectly fit any of the previously described LRR subfamilies. By applying
protein sequence analysis and structural prediction, we clarify this ambiguous case of LRR classification and assign GALA-
LRRs to CC-LRR subfamily. We demonstrate that side-by-side packing of LRRs in the 3D structures may control the limits of
repeat variability within the LRR subfamilies during evolution. The LRR packing can be used as a criterion, complementing
the repeat sequences, to classify newly identified LRR domains. Our phylogenetic analysis of F-box domains proposes the
lateral gene transfer of bacterial GALA proteins from host plants. We also present an evolutionary scenario which can
explain the transformation of the original plant LRRs into slightly different bacterial LRRs. The examination of the selective
evolutionary pressure acting on GALA proteins suggests that the convex side of their horse-shoe shaped LRR domains is
more prone to positive selection than the concave side, and we therefore hypothesize that the convex surface might be the
site of protein binding relevant to the adaptor function of the F-box GALA proteins. This conclusion provides a strong


Source: Anisimova, Maria - Institute of Scientific Computing, Eidgenössische Technische Hochschule Zürich (ETHZ)
Ecole Polytechnique, Centre de mathématiques


Collections: Biology and Medicine; Mathematics