PMID: 18406424 , Related PDB id: 2QIM

Authors:

Fernandes H, Pasternak O, Bujacz G, Bujacz A, Sikorski MM, Jaskolski M

Title:

Lupinus luteus pathogenesis-related protein as a reservoir for cytokinin.

Journal:

J Mol Biol. 2008 May 16;378(5):1040-51. Epub 2008 Mar 19.

Abstract:

Plant pathogenesis-related (PR) proteins of class 10 (PR-10) are small and cytosolic. The main feature of their three-dimensional structure is a large cavity between a seven-stranded antiparallel beta-sheet and a long C-terminal alpha-helix. Although PR-10 proteins are abundant in plants, their physiological role remains unknown. Recent data have indicated ligand binding as their possible biological function. The article describes the structure of a complex between a classic PR-10 protein (yellow lupine LlPR-10.2B) and the plant hormone, trans-zeatin. Previously, trans-zeatin binding has been reported in a structurally related cytokinin-specific binding protein, which has a distant sequence relation with classic PR-10 proteins. In the present 1.35 A resolution crystallographic model, three perfectly ordered zeatin molecules are found in the binding cavity of the protein. The fact that three zeatin molecules are bound by the protein when only a fourfold molar excess of the ligand was used indicates an unusual type of affinity for this ligand and suggests that LlPR-10.2B, and perhaps other PR-10 proteins as well, acts as a reservoir of cytokinin molecules in the aqueous environment of the cell.