PDBsum entry 1m45

Cell cycle protein

PDB id: 1m45

Contents

Protein chains

142 a.a. *

25 a.a. *

Waters ×252

* Residue conservation analysis

PDB id:

1m45

Name:

Cell cycle protein

Title:

Crystal structure of mlc1p bound to iq2 of myo2p, a class v myosin

Structure:

Myosin light chain. Chain: a. Synonym: mlc1p. Engineered: yes. Iq2 motif from myo2p, a class v myosin. Chain: b. Synonym: iq2. Engineered: yes

Source:

Saccharomyces cerevisiae. Baker's yeast. Organism_taxid: 4932. Gene: mlc1. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008. Synthetic: yes. Other_details: the peptide was chemically synthesized. The sequence of the peptide is naturally found in saccharomyces cerevisiae

Biol. unit:

Dimer (from PQS)

Resolution:

1.65Å R-factor: 0.193 R-free: 0.228

Authors:

M.Terrak,R.Dominguez

Key ref:

M.Terrak et al. (2003). Two distinct myosin light chain structures are induced by specific variations within the bound IQ motifs-functional implications. EMBO J, 22, 362-371. PubMed id: 12554638 DOI: 10.1093/emboj/cdg058

Date:

02-Jul-02 Release date: 11-Feb-03

Protein chain

P53141  (MLC1_YEAST) -  Myosin light chain 1 from Saccharomyces cerevisiae (strain ATCC 204508 / S288c)

Seq: 149 a.a.

Struc: 142 a.a.

Protein chain

P19524  (MYO2_YEAST) -  Myosin-2 from Saccharomyces cerevisiae (strain ATCC 204508 / S288c)

Seq: 1574 a.a.

Struc: 25 a.a.

DOI no: 10.1093/emboj/cdg058

EMBO J 22:362-371 (2003)

PubMed id: 12554638

Two distinct myosin light chain structures are induced by specific variations within the bound IQ motifs-functional implications.

M.Terrak, G.Wu, W.F.Stafford, R.C.Lu, R.Dominguez.

ABSTRACT

IQ motifs are widespread in nature. Mlc1p is a calmodulin-like myosin light chain that binds to IQ motifs of a class V myosin, Myo2p, and an IQGAP-related protein, Iqg1p, playing a role in polarized growth and cytokinesis in Saccharomyces cerevisiae. The crystal structures of Mlc1p bound to IQ2 and IQ4 of Myo2p differ dramatically. When bound to IQ2, Mlc1p adopts a compact conformation in which both the N- and C-lobes interact with the IQ motif. However, in the complex with IQ4, the N-lobe no longer interacts with the IQ motif, resulting in an extended conformation of Mlc1p. The two light chain structures relate to two distinct subfamilies of IQ motifs, one of which does not interact with the N-lobes of calmodulin-like light chains. The correlation between light chain structure and IQ sequence is demonstrated further by sedimentation velocity analysis of complexes of Mlc1p with IQ motifs from Myo2p and Iqg1p. The resulting 'free' N-lobes of myosin light chains in the extended conformation could mediate the formation of ternary complexes during protein localization and/or partner recruitment.

Selected figure(s)

Figure 1.
Figure 1 Ribbon diagram of the structures of Mlc1p bound to IQ2 and IQ4 of Myo2p. (A) Compact structure of the Mlc1p -IQ2 complex. The N-lobe, the C-lobe and the IQ peptide are shown in blue, red and green, respectively (this color scheme is kept through all the figures). (B) Extended structure of the Mlc1p -IQ4 complex. (C) Superimposition of the structures of Mlc1p -IQ2 and Mlc1p -IQ4 (thinner trace). (D) Superimposition of the structures of Mlc1p -IQ2 with those of ELC -IQ complexes from scallop (yellow) and smooth muscle (pink) myosins (Xie et al., 1994; Houdusse and Cohen, 1996; Dominguez et al., 1998). Note how differences in the orientation of the N-lobes are mirrored by differences in the orientation of the C-terminal portions of the IQ motifs. (E) Superimposition of the extended structures of Mlc1p -IQ4 and scallop RLC -IQ (cyan) complexes. The myosin heavy chain fragment (yellow) bound to the scallop RLC is bent by 90°. The Mg2+-bound (and fully open) N-lobe of the RLC binds to a conserved sequence (WQWWKLYSKVKPLL) of the myosin heavy chain that follows immediately after the 90° turn. Note that this N-lobe-specific target sequence does not make up part of a canonical IQ motif.

Figure 5.
Figure 5 IQ motif-binding interface of Mlc1p. (A) Compact conformation of the Mlc1p -IQ2 complex. The view is along the axis of the -helices of IQ2 (shown in green). The amino acids of Mlc1p are colored yellow, except for those amino acids that make direct contacts with the IQ peptide, which are depicted in red (the same amino acids are also colored red in Figure 3A). Two views are shown: on the left side of the figure, the IQ peptide has been moved out of its binding cleft manually to illustrate better the binding interface, while the view on the right side corresponds to the actual position of the IQ peptide in the crystal structure. (B) Extended structure of Mlc1p -IQ4 (same color scheme and orientation as A). Note how all of the amino acids of the N-lobe that interact with IQ2 in the compact structure become solvent exposed in this complex. The resulting surface would be available for interactions with a GxxxR-containing target without a need for the N-lobe to open.

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: EMBO J (2003, 22, 362-371) copyright 2003.

Figures were selected by the author.