PDBsum entry 3fex

Translation, protein transport

PDB id: 3fex

Contents

Protein chains

756 a.a. *

80 a.a. *

423 a.a. *

* Residue conservation analysis

PDB id:

3fex

Name:

Translation, protein transport

Title:

Crystal structure of the cbc-importin alpha complex.

Structure:

Nuclear cap-binding protein subunit 1. Chain: a. Synonym: cap binding protein 80. 80 kda nuclear cap-binding protein. Ncbp 80 kda subunit. Cbp80. Engineered: yes. Nuclear cap-binding protein subunit 2. Chain: b. Synonym: cap binding protein 20. 20 kda nuclear cap-binding protein, ncbp 20 kda subunit, cbp20, ncbp-interacting protein 1, nip1, cell

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: cbp80, ncbp, ncbp1. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108. Gene: cbp20, ncbp2, pig55. Gene: kpna2, rch1, srp1. Expressed in: escherichia coli.

Resolution:

3.55Å R-factor: 0.221 R-free: 0.292

Authors:

S.M.G.Dias,A.L.B.Ambrosio,R.A.Cerione

Key ref:

S.M.Dias et al. (2009). The molecular basis for the regulation of the cap-binding complex by the importins. Nat Struct Biol, 16, 930-937. PubMed id: 19668212 DOI: 10.1038/nsmb.1649

Date:

01-Dec-08 Release date: 11-Aug-09

Protein chain

Q09161  (NCBP1_HUMAN) -  Nuclear cap-binding protein subunit 1 from Homo sapiens

Seq: 790 a.a.

Struc: 756 a.a.

Protein chain

P52298  (NCBP2_HUMAN) -  Nuclear cap-binding protein subunit 2 from Homo sapiens

Seq: 156 a.a.

Struc: 80 a.a.

Protein chain

P52292  (IMA1_HUMAN) -  Importin subunit alpha-1 from Homo sapiens

Seq: 529 a.a.

Struc: 423 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1038/nsmb.1649

Nat Struct Biol 16:930-937 (2009)

PubMed id: 19668212

The molecular basis for the regulation of the cap-binding complex by the importins.

S.M.Dias, K.F.Wilson, K.S.Rojas, A.L.Ambrosio, R.A.Cerione.

ABSTRACT

The binding of capped RNAs to the cap-binding complex (CBC) in the nucleus, and their dissociation from the CBC in the cytosol, represent essential steps in RNA processing. Here we show how the nucleocytoplasmic transport proteins importin-alpha and importin-beta have key roles in regulating these events. As a first step toward understanding the molecular basis for this regulation, we determined a 2.2-A resolution X-ray structure for a CBC-importin-alpha complex that provides a detailed picture for how importin-alpha binds to the CBP80 subunit of the CBC. Through a combination of biochemical studies, X-ray crystallographic information and small-angle scattering experiments, we then determined how importin-beta binds to the CBC through its CBP20 subunit. Together, these studies enable us to propose a model describing how importin-beta stimulates the dissociation of capped RNA from the CBC in the cytosol following its nuclear export.

Selected figure(s)

Figure 1.
X-ray crystal structure of the CBC–importin- IBB complex. CBP80 is shown as a surface (gray), whereas CBP20 and importin- are depicted by ribbon diagrams (orange and green, respectively). Shown above in stereoview is the N-terminal region of CBP80, residues 2–22 (represented by sticks), which contains the NLS segment of this protein, along with its 2F[o] – F[c] map contoured at 1 .

Figure 3.
(a) Surface (CBP80) and ribbon (CBP20) representations of the CBC (PDB 1N52 (ref. 27)) illustrate the stabilization of the N-terminal hinge of CBP20 by residues in its binding groove within CBP80. The N-terminal region of CBP20 (which includes residues Ser11, Asp12 and Ser13, shown in dark blue) enters a groove formed by residues Lys327 and Glu328 of CBP80 (green), making contacts that stabilize residues of CBP20 in loop 2- 3 (magenta) in the cap-bound conformation. The inset shows these interactions in detail. Residues 26–36 of the N-terminal region of CBP80 are in black. (b) HeLa cells were transiently transfected with constructs encoding V5-CBP80 or V5-CBP80-K327A E328A and HA-CBP20, as indicated, for 24 h. The expressed CBP80 proteins were immunoprecipitated with anti-V5 and western blotted with anti-HA to show that CBP20 co-imunoprecipitated equally well with wild-type and mutated CBP80 (as quantified by densitometry). Immunoprecipitated CBC was assayed for UV cross-linking incorporation of [ ^32P]GTP (c) and ^32P-labeled capped mRNA (d), with and without an excess of cap.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Biol (2009, 16, 930-937) copyright 2009.

Figures were selected by an automated process.