title: Crystal structures of the signal transducing protein GlnK from Thermus thermophilus HB8.
abstract: The Thermus thermophilus HB8 genome encodes a signal transducing PII protein, GlnK. The crystal structures of GlnK have been determined in two different space groups, P2(1)2(1)2(1) and P3(1)21. The PII protein has the T-loop, which is essential for interactions with receptor proteins. In both crystal forms, three GlnK molecules form a trimer in the asymmetric unit. In one P2(1)2(1)2(1) crystal form, the three T-loops in the trimer are disordered, while in another P2(1)2(1)2(1) crystal form, the T-loop from one molecule in the trimer is ordered. In the P3(1)21 crystal, one T-loop is ordered while the other two T-loops are disordered. The conformations of the ordered T-loops significantly differ between the two crystal forms; one makes the alpha-helix in the middle of the T-loop, while the other has an extension of the beta-hairpin. Two different conformations are captured by the crystal contacts. The observation of multiple T-loop conformations suggests that the T-loop could potentially exhibit "polysterism," which would be important for interactions with receptor proteins. The crystal structures of the nucleotide-bound forms, GlnK.ATP and GlnK.ADP, have also been determined. ATP/ADP binding within a cleft at the interface of two adjacent T. thermophilus GlnK monomers might affect the conformation of the T-loop.
authors.affiliation: Protein Research Group, RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sakai
authors.forename: Hongfei
authors.initials: H
authors.lastname: Wang
authors.forename: Chie
authors.initials: C
authors.lastname: Takemoto-Hori
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kaminishi
authors.forename: Hiroto
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kamewari
authors.forename: Takaho
authors.initials: T
authors.lastname: Terada
authors.forename: Seiki
authors.initials: S
authors.lastname: Kuramitsu
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D051922:PII Nitrogen Regulatory Proteins; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D016963:Thermus thermophilus / Q000737:chemistry*; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate