PDBsum entry 1tki

Serine kinase

PDB id: 1tki

Contents

Protein chains

321 a.a. *

Waters ×514

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Structural basis for activation of the titin kinase domain during myofibrillogenesis.

Authors

O.Mayans, P.F.Van der ven, M.Wilm, A.Mues, P.Young, D.O.Fürst, M.Wilmanns, M.Gautel.

Ref.

Nature, 1998, 395, 863-869. [DOI no: 10.1038/27603]

PubMed id

9804419

Abstract

The giant muscle protein titin (connectin) is essential in the temporal and spatial control of the assembly of the highly ordered sarcomeres (contractile units) of striated muscle. Here we present the crystal structure of titin's only catalytic domain, an autoregulated serine kinase (titin kinase). The structure shows how the active site is inhibited by a tyrosine of the kinase domain. We describe a dual mechanism of activation of titin kinase that consists of phosphorylation of this tyrosine and binding of calcium/calmodulin to the regulatory tail. The serine kinase domain of titin is the first known non-arginine-aspartate kinase to be activated by phosphorylation. The phosphorylated tyrosine is not located in the activation segment, as in other kinases, but in the P + 1 loop, indicating that this tyrosine is a binding partner of the titin kinase substrate. Titin kinase phosphorylates the muscle protein telethonin in early differentiating myocytes, indicating that this kinase may act in myofibrillogenesis.

Figure 2.
Figure 2 Titin kinase constructs used in this study. The domain pattern of the kinase region of human titin and the residues of the respective constructs are shown. Fn3, fibronectin-III-like domain; Ig, immunoglobulin like domain. a, Kin4 lacks the regulatory tail (RT), leaving a constitutively active catalytic core. The kin1 construct includes the regulatory tail. The N-terminal phasing is based on the N termini of DAP kinase^31 and of Dictyostelium discoideum MLCK42. b, Two-hybrid screens of human skeletal and cardiac complementary DNA libraries with kin4 and kin4(K36A) yield multiple overlapping clones from the regulatory tail, showing that there is a functional binding site in the active site of kin4. The strength of interaction is given by HIS3 signals and by -galactosidase activity30. The first residue in the cardiac titin sequence of three representative clones is shown at the left.

Figure 4.
Figure 4 Active-site conformation of the autoinhibited forms of titin kinase, twitchin and IRK. a, The active site of titin kinase. The guanidinium group of R129 forms short hydrogen bonds with the side chains of D127 and Y170 from the P+ 1 loop. There is a weak direct hydrogen bond between D127 and Y170 (3.1 ring in length). D127 forms further hydrogen bonds with Q150. b, Twitchin active site^10. The catalytic aspartate, D174 forms hydrogen bonds with K176, Q200 and R355 from the regulatory tail. At the position of Y170 in titin kinase, there is an alanine in twitchin. In the autoinhibited twitchin structure^10, the catalytic aspartate is blocked by a salt bridge with an arginine (R355 in twitchin) of the regulatory tail, suggesting a different activation mechanism than for titin kinase. In titin kinase, the equivalent arginine, R306, does not interact with the catalytic aspartate. c, Active site of the autoinhibited form of IRK17. The catalytic aspartate, D1132, is bound to Y1162. This bond is disrupted after phosphorylation of Y1162, accompanied by phosphorylation of two other tyrosines and induces a conformational change of the activation segment from a closed to an open conformation25. The colour codes of the tubes are as in Fig. 3a. d, Stereo view of a 2F[o] - F[c] electron-density map, using phases of the final model, contoured at 1.3 . The electron density shown covers several active-site residues and solvent molecules. Some titin-kinase residues are labelled. a-c were prepared with GRASP45 and d with program O (ref. 46).

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (1998, 395, 863-869) copyright 1998.

Secondary reference #1

Title

X-Ray analysis of protein crystals with thin plate morphology

Authors

O.Mayans, M.Wilmanns.

Ref.

TO BE PUBLISHED ...