PDBsum entry 1w9c

Nuclear protein

PDB id: 1w9c

Contents

Protein chains

321 a.a. *

Waters ×192

* Residue conservation analysis

PDB id:

1w9c

Name:

Nuclear protein

Title:

Proteolytic fragment of crm1 spanning six c-terminal heat repeats

Structure:

Crm1 protein. Chain: a, b. Fragment: c-terminal six heat repeats, residues 707-1027. Synonym: exportin 1. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

2.30Å R-factor: 0.229 R-free: 0.277

Authors:

C.Petosa,G.Schoehn,P.Askjaer,U.Bauer,M.Moulin,U.Steuerwald,M.Soler- Lopez,F.Baudin,I.W.Mattaj,C.W.Muller

Key ref:

C.Petosa et al. (2004). Architecture of CRM1/Exportin1 suggests how cooperativity is achieved during formation of a nuclear export complex. Mol Cell, 16, 761-775. PubMed id: 15574331 DOI: 10.1016/j.molcel.2004.11.018

Date:

08-Oct-04 Release date: 03-Dec-04

Protein chains

O14980  (XPO1_HUMAN) -  Exportin-1 from Homo sapiens

Seq: 1071 a.a.

Struc: 321 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.molcel.2004.11.018

Mol Cell 16:761-775 (2004)

PubMed id: 15574331

Architecture of CRM1/Exportin1 suggests how cooperativity is achieved during formation of a nuclear export complex.

C.Petosa, G.Schoehn, P.Askjaer, U.Bauer, M.Moulin, U.Steuerwald, M.Soler-López, F.Baudin, I.W.Mattaj, C.W.Müller.

ABSTRACT

CRM1/Exportin1 mediates the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES) by forming a cooperative ternary complex with the NES-bearing substrate and the small GTPase Ran. We present a structural model of human CRM1 based on a combination of X-ray crystallography, homology modeling, and electron microscopy. The architecture of CRM1 resembles that of the import receptor transportin1, with 19 HEAT repeats and a large loop implicated in Ran binding. Residues critical for NES recognition are identified adjacent to the cysteine residue targeted by leptomycin B (LMB), a specific CRM1 inhibitor. We present evidence that a conformational change of the Ran binding loop accounts for the cooperativity of Ran- and substrate binding and for the selective enhancement of CRM1-mediated export by the cofactor RanBP3. Our findings indicate that a single architectural and mechanistic framework can explain the divergent effects of RanGTP on substrate binding by many import and export receptors.

Selected figure(s)

Figure 2.
Figure 2. HEAT Repeats in CRM1(A) Sequence alignment between the middle regions of CRM1 and Trn1. Identically and highly conserved residues are in inverse font and highlighted in gray, respectively. The chymotrypsin cleavage site marks the beginning of the C-terminal 70 kDa fragment. Colored bars indicate helices observed from crystal structures; predicted helices are in gray. The LMB site and residues implicated in RanBP3 binding are indicated. Sequence numbering is that of human Trn1 (top) and human CRM1 (bottom).(B) HEAT-repeat maps. CRM1 is predicted to contain the same number of repeats as Trn1 and Impβ. The difference in sequence length is due to CRM1 having larger individual repeats (primarily repeats 1, 3, 7, 13, 15, and 19) and a long tail region. The C-terminal region of Trn1 sometimes designated repeat 20 is labeled “C.” The hashed bar shows where the mapping is uncertain.

Figure 6.
Figure 6. Predicted Structure of the Central Conserved Region and Proposed Cooperativity Model(A) Close-up of the LMB and putative NES binding sites. Cys528 is predicted to pack against residues Leu525 and Phe572 and against the aliphatic moiety of Lys568. The acidic loop of Trn1 is superposed to give an approximate idea of the path of the Ran binding loop in CRM1. A helices are in red, B in yellow.(B) CRM1 structural model showing repeats 8–19 and summary of mutations. Residues mentioned in the text are indicated. B helices are in yellow; A helices and helix 19′ are in gray. Strain crm1-N1 has two point mutations, G503D and M546I (G502 and M545 in human CRM1). Met545 is adjacent to Cys528 and is half a helical turn away from Ile547, which packs against Gly502.(C) C-terminal arch of Trn1 showing the path of the acidic loop.(D) Comparison of Ran-mediated cargo dissociation by Trn1 with proposed cooperativity model of CRM1. Only the conformational changes within the Ran binding loop are shown; the HEAT repeats might also change conformation upon ligand binding. The masking conformation of CRM1 (top of scheme) is putatively stabilized or destabilized in the class 1b and 1a mutants, respectively.

The above figures are reprinted by permission from Cell Press: Mol Cell (2004, 16, 761-775) copyright 2004.

Figures were selected by the author.