Figure 2.

A structural model of the activated BRI1 kinase domain. Shown here are three (0°, 60°, and 180°) rotational views of a rainbow-colored ribbon model of the crystal structure of the BRI1 kinase domain (Protein Data Bank No. 4oh4). Individual α-helices (αB-αI) and β-strands (β1-β5) were labelled. The magenta-colored sticks indicate phosphorylated Ser/Thr residues with the magenta dots surrounding Ser¹⁰⁴⁴ and Thr¹⁰⁴⁹ of the activation segment, the green sticks denote the Lys⁹¹¹ and Glu⁹²⁷ residues that form the salt bridge between the β3-strand and αC-helix, the red sticks mark the three positively charged residues of the phosphate-binding pocket, and the orange sticks represent the phosphorylated Tyr residue. The red spheres show adenylyl-imidodiphosphate (a non-hydrolysable ATP analog), the orange spheres indicate the gatekeeper Tyr⁹⁵⁶ residue that is also phosphorylated in in vitro assays, and the light-blue spheres denote the five regulatory-spine (R-spine) residues (from lower to upper: Asp¹⁰⁶⁸, His¹⁰⁷⁷, Phe¹⁰²⁸, Ile⁹³¹, and Leu⁹⁴²). The rainbow bar indicates the order of amino acids (AAs) from the N-terminus (blue) to the C-terminus (red).