PDBsum entry: 1sjj

Contractile protein

PDB id: 1sjj

Contents

Protein chains

863 a.a. *

* Residue conservation analysis

PDB id:

1sjj

Name:

Contractile protein

Title:

Cryo-em structure of chicken gizzard smooth muscle alpha- actinin

Structure:

Actinin. Chain: a, b

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Other_details: protein isolated from chicken gizzards

Biol. unit:

Dimer (from PQS)

Authors:

J.Liu,D.W.Taylor,K.A.Taylor

Key ref:

J.Liu et al. (2004). A 3-D reconstruction of smooth muscle alpha-actinin by CryoEm reveals two different conformations at the actin-binding region. J Mol Biol, 338, 115-125. PubMed id: 15050827 DOI: 10.1016/j.jmb.2004.02.034

Date:

03-Mar-04 Release date: 23-Mar-04

Protein chains

P05094  (ACTN1_CHICK) -  Alpha-actinin-1

Seq: 893 a.a.

Struc: 863 a.a.*

* PDB and UniProt seqs differ at 13 residue positions (black crosses)

 Gene Ontology (GO) functional annotation 

• Cellular component: membrane (11 terms)
• Biological process: actin filament bundle assembly (1 term)
• Biochemical function: protein binding (4 terms)

DOI no: 10.1016/j.jmb.2004.02.034

J Mol Biol 338:115-125 (2004)

PubMed id: 15050827

A 3-D reconstruction of smooth muscle alpha-actinin by CryoEm reveals two different conformations at the actin-binding region.

J.Liu, D.W.Taylor, K.A.Taylor.

ABSTRACT

Cryoelectron microscopy was used to obtain a 3-D image at 2.0 nm resolution of 2-D arrays of smooth muscle alpha-actinin. The reconstruction reveals a well-resolved long central domain with 90 degrees of left-handed twist and near 2-fold symmetry. However, the molecular ends which contain the actin binding and calmodulin-like domains, have different structures oriented approximately 90 degrees to each other. Atomic structures for the alpha-actinin domains were built by homology modeling and assembled into an atomic model. Model building suggests that in the 2-D arrays, the two calponin homology domains that comprise the actin-binding domain have a closed conformation at one end and an open conformation at the other end due to domain swapping. The open and closed conformations of the actin-binding domain suggests flexibility that may underlie Ca2+ regulation. The approximately 90 degrees orientation difference at the molecular ends may underlie alpha-actinin's ability to crosslink actin filaments in nearly any orientation.

Selected figure(s)

Figure 4.
Figure 4. Paired and free ends aligned to R1 and R4. A and B, Paired and free ends looking approximately perpendicular to the plane of the 2-D array. C and D, Paired and free ends looking down the axis of the R1-R4 domain. In A and B the orientation of the R1-R4 domain is identical in both views and is similarly identical in C and D. Note the 90° orientation difference in the ABD in C and D.

Figure 5.
Figure 5. Models for polar and bipolar actin crosslinking. A and C, are longitudinal and axial views of the polar crosslink model produced using modified paired end conformations for the a-actinin ends. B and D, Longitudinal and axial views of the bipolar crosslink model produced using free end conformations for the a-actinin ends. The color scheme is CH1 (magenta), CH2 (red), R1-R4 (cyan) and Cam (yellow). The actin filament is green. In B and D the titin Z7 repeat is colored blue. In the polar crosslinking model, the ABD was changed from the open conformation that fit the map to a closed orientation suitable for actin binding. In addition, one ABD was reoriented so that the actin filaments could be coplanar. The a-actinin model in this case has no symmetry. In the bipolar crosslinking model, there are minimal changes from the reconstruction model and the model. The model has only near 2-fold rotational symmetry because 2-fold symmetry was not enforced for the R1-R4 domain.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2004, 338, 115-125) copyright 2004.

Figures were selected by the author.