Crystal structure of human JAK3 kinase domain complex and binding pockets thereof

A method for identifying a candidate inhibitor using a human Janus Kinase 3 crystal comprising a human Janus Kinase 3 protein,

• wherein said human Janus Kinase 3 protein consists of amino acid residues 810-1115 of SEQ ID NO:
• 1,
• wherein said human Janus Kinase 3 protein comprises a kinase domain,
• wherein said human Janus Kinase 3 kinase domain is in complex with a chemical entity selected from the group consisting of adenosine, ATP, an ATP analogue, AMP-PNP, a nucleotide triphosphate, a nucleotide diphosphate, and phosphate, and wherein said crystal is characterized by either:
• (i) space group P21 and has unit cell parameters of a=59.98±4 Å, b=90.19±4 Å, c=69.00±4 Å, α=90°, β=111.5°, γ=90°, or (ii) space group P212121 and has unit cell parameters of a=72.36±4 Å, b=90.04±4 Å, c=105.60±4 Å, α=β=γ=90°,
• wherein said method comprises:
• (a) soaking said human Janus Kinase 3 crystal in the presence of said candidate inhibitor thereby displacing said chemical entity and generating a human Janus Kinase 3 crystal comprising a human Janus Kinase 3 kinase domain in complex with said candidate inhibitor;
• (b) determining the three-dimensional structure coordinates of human Janus Kinase 3 using the crystal in step (a);
• (c) using the structure coordinates from step (b) to generate a three-dimensional structure of a molecular complex comprising a binding site of amino acid residues Gln827, Leu828, Gly829, Lys830, Gly831, Asn832, Phe833, Gly834, Ser835, Val836, Glu837, Leu838, Val852, Ala853, Val854, Lys855, Gln856, Leu857, Val884, Lys885, Tyr886, Leu900, Val901, Met902, Glu903, Tyr904, Leu905, Pro906, Ser907, Gly908, Cys909, Leu910, Arg911, Asp912, His947, Asp949, Leu950, Ala951, Ala952, Arg953, Asn954, Ile955, Leu956, Val957, Ala966, Asp967, Leu970, Glu985, Gln988, Ser989, Pro990 and Trp993 according to Table 2, wherein the root mean square deviation of the backbone atoms is not greater than about 2.5 Å;
• and
• (d) contacting said candidate inhibitor with human Janus Kinase 3 to determine the ability of said candidate inhibitor to bind to human Janus Kinase 3.