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Crystal structures of the signal transducing protein GlnK from Thermus thermophilus HB8

2004; Elsevier BV; Volume: 149; Issue: 1 Linguagem: Inglês

10.1016/j.jsb.2004.08.007

1095-8657

Hiroaki Sakai, Hongfei Wang, Chie Takemoto‐Hori, Tatsuya Kaminishi, Hiroto Yamaguchi, Yuki Kamewari, Takaho Terada, Seiki Kuramitsu, Mikako Shirouzu, Shigeyuki Yokoyama,

Protein Kinase Regulation and GTPase Signaling

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, P212121 and P3121. 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 P212121 crystal form, the three T-loops in the trimer are disordered, while in another P212121 crystal form, the T-loop from one molecule in the trimer is ordered. In the P3121 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 α-helix in the middle of the T-loop, while the other has an extension of the β-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.