PDBsum entry 1oqp

Protein binding

PDB id: 1oqp

Contents

Protein chains

77 a.a. *

19 a.a. *

* Residue conservation analysis

PDB id:

1oqp

Name:

Protein binding

Title:

Structure of the ca2+/c-terminal domain of caltractin in complex with the cdc31p-binding domain from kar1p

Structure:

Caltractin. Chain: a. Synonym: centrin, 20 kda calcium-binding protein. Engineered: yes. Cell division control protein kar1. Chain: b. Engineered: yes

Source:

Chlamydomonas reinhardtii. Organism_taxid: 3055. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Other_details: the peptide consists of the cdc31p-binding domain from kar1p, residues 239-257, and has been chemically synthesized using solid phase f-moc chemistry. The sequence is naturally found in saccharomyces cerevisiae (baker's yeast).

NMR struc:

20 models

Authors:

H.T.Hu,W.J.Chazin

Key ref:

H.Hu and W.J.Chazin (2003). Unique features in the C-terminal domain provide caltractin with target specificity. J Mol Biol, 330, 473-484. PubMed id: 12842464 DOI: 10.1016/S0022-2836(03)00619-3

Date:

10-Mar-03 Release date: 24-Jun-03

Protein chain

P05434  (CATR_CHLRE) -  Caltractin from Chlamydomonas reinhardtii

Seq: 169 a.a.

Struc: 77 a.a.*

Protein chain

P11927  (KAR1_YEAST) -  Cell division control protein KAR1 from Saccharomyces cerevisiae (strain ATCC 204508 / S288c)

Seq: 433 a.a.

Struc: 19 a.a.

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1016/S0022-2836(03)00619-3

J Mol Biol 330:473-484 (2003)

PubMed id: 12842464

Unique features in the C-terminal domain provide caltractin with target specificity.

H.Hu, W.J.Chazin.

ABSTRACT

Caltractin (centrin) is a member of the calmodulin (CaM) superfamily of EF-hand calcium-binding proteins. It is an essential component of the centrosomal structures in a wide range of organisms. Caltractin and calmodulin apparently function in distinct calcium signaling pathways despite substantial sequence similarity. In an effort to understand the structural basis for such differences, the high-resolution three-dimensional solution structure of the complex between the Ca(2+)-activated C-terminal domain of Chlamydomonas reinhardtii caltractin (CRC-C) and a 19 residue peptide fragment comprising the putative cdc31p-binding region of Kar1p (K(19)) has been determined by multi-dimensional heteronuclear NMR spectroscopy. Formation of the complex is calcium-dependent and is stabilized by extensive interactions between CRC-C and three key hydrophobic anchors (Trp10, Leu13 and Leu14) in the peptide as well as favorable electrostatic interactions at the protein-peptide interface. In-depth comparisons have been made to the structure of the complex of Ca(2+)-activated calmodulin and R(20), the CaM-binding domain of smooth muscle myosin light-chain kinase. Although the overall structures of CRC and CaM domains in their respective complexes are very similar, differences in critical regions in the sequences of these proteins and their targets lead to clear differences in the complementarity of their respective binding surfaces. These subtle differences reveal the structural basis for the Ca(2+)-dependent regulation of distinct cellular signaling events by CRC and CaM.

Selected figure(s)

Figure 1.
Figure 1. Stereo view of the final family of 20 conformers representing the structure of CRC-C in complex with K[19] (PDB entry code 1OQP). The protein is shown in blue, and the K[19] peptide in red. The first six residues of CRC-C are highly disordered and not shown here. Superposition of the structures was based on the backbone atoms of the secondary structural elements in CRC-C and K[19] defined as: (CRC-C) helix I, 99-110; b-strand I, 117-119; helix II, 120-130; helix III, 136-146; b-strand II, 153-155; helix IV, 156-165; (K[19]) helix I', 5-15.

Figure 3.
Figure 3. Detailed comparison of the CRC-C/K[19] and CaM/R[20] complexes (PDB entry codes 1OQP and 1CDL, respectively). (a) Ribbon representation of the superimposed structures of CRC-C (blue) and CaM (red) complexes. The overlay is based on the secondary structural elements in CRC-C and CaM-C. For clarity, the N-terminal domain of CaM is not displayed. (b) Comparison of intermolecular contacts between K[19] and CRC-C to those between R[20] and CaM-C. Residues within 7 Å are considered to be in contact. The peptides are aligned on the basis of the common tryptophan residue. The helical portions of the peptides are drawn in continuous lines, and the disordered regions in broken lines. Note that two residues at the N terminus of K[19] and two C-terminal residues of R[20] have been removed for clarity. The three anchoring residues in K[19] (Trp10, Leu13, Leu14) and the corresponding Trp5, Thr8, and Gly9 in R[20] are highlighted in red. The additional hydrophobic anchor in R[20] (Val12) and the corresponding residue in K[19] (Asp17) are highlighted in green. The pseudo numbering scheme used to align the homologous residues in CRC-C and CaM-C subtracts 92 and 74 from the CRC and the CaM residue numbers, respectively. Contacts involving homologous residues in the two complexes are indicated by red lettering. (c) Overlay of the structures of CRC-C (blue) and CaM-C (red) from their respective complexes. The side-chains of methionine and phenylalanine residues in CaM-C and the corresponding residues in CRC-C are highlighted. The superposition was made using the backbone heavy atoms of the helices only. (d) Comparison of the hydrophobic molecular surfaces (upper panel) and the electrostatic potential surfaces (lower panel) of CRC-C and CaM-C. The deep hydrophobic pockets accommodating the tryptophan residues on the surfaces of both proteins are indicated by the thick arrows. The additional hydrophobic pocket accommodating Leu13 in K[19] on the surface of CRC-C is indicated by the wavy arrow. A positively charged patch unique to CRC-C is indicated by the circle.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2003, 330, 473-484) copyright 2003.

Figures were selected by the author.