PDBsum entry 2fsn

Structural protein

PDB id: 2fsn

Contents

Protein chains

310 a.a. *

Ligands

ADP ×2

Metals

_MG ×2

Waters ×9

* Residue conservation analysis

PDB id:

2fsn

Name:

Structural protein

Title:

Crystal structure of ta0583, an archaeal actin homolog, complex with adp

Structure:

Hypothetical protein ta0583. Chain: a, b. Engineered: yes

Source:

Thermoplasma acidophilum. Organism_taxid: 273075. Strain: dsm 1728. Gene: ta0583. Expressed in: escherichia coli bl21. Expression_system_taxid: 511693.

Resolution:

2.90Å R-factor: 0.283 R-free: 0.359

Authors:

A.Roeben,C.Kofler,I.Nagy,S.Nickell,F.Ulrich Hartl,A.Bracher

Key ref:

A.Roeben et al. (2006). Crystal structure of an archaeal actin homolog. J Mol Biol, 358, 145-156. PubMed id: 16500678 DOI: 10.1016/j.jmb.2006.01.096

Date:

23-Jan-06 Release date: 18-Apr-06

Protein chains

Q9HKL4  (ACTH_THEAC) -  Archaeal actin homolog from Thermoplasma acidophilum (strain ATCC 25905 / DSM 1728 / JCM 9062 / NBRC 15155 / AMRC-C165)

Seq: 326 a.a.

Struc: 310 a.a.

DOI no: 10.1016/j.jmb.2006.01.096

J Mol Biol 358:145-156 (2006)

PubMed id: 16500678

Crystal structure of an archaeal actin homolog.

A.Roeben, C.Kofler, I.Nagy, S.Nickell, F.U.Hartl, A.Bracher.

ABSTRACT

Prokaryotic homologs of the eukaryotic structural protein actin, such as MreB and ParM, have been implicated in determination of bacterial cell shape, and in the segregation of genomic and plasmid DNA. In contrast to these bacterial actin homologs, little is known about the archaeal counterparts. As a first step, we expressed a predicted actin homolog of the thermophilic archaeon Thermoplasma acidophilum, Ta0583, and determined its crystal structure at 2.1A resolution. Ta0583 is expressed as a soluble protein in T.acidophilum and is an active ATPase at physiological temperature. In vitro, Ta0583 forms sheets with spacings resembling the crystal lattice, indicating an inherent propensity to form filamentous structures. The fold of Ta0583 contains the core structure of actin and clearly belongs to the actin/Hsp70 superfamily of ATPases. Ta0583 is approximately equidistant from actin and MreB on the structural level, and combines features from both eubacterial actin homologs, MreB and ParM. The structure of Ta0583 co-crystallized with ADP indicates that the nucleotide binds at the interface between the subdomains of Ta0583 in a manner similar to that of actin. However, the conformation of the nucleotide observed in complex with Ta0583 clearly differs from that in complex with actin, but closely resembles the conformation of ParM-bound nucleotide. On the basis of sequence and structural homology, we suggest that Ta0583 derives from a ParM-like actin homolog that was once encoded by a plasmid and was transferred into a common ancestor of Thermoplasma and Ferroplasma. Intriguingly, both genera are characterized by the lack of a cell wall, and therefore Ta0583 could have a function in cellular organization.

Selected figure(s)

Figure 1.
Figure 1. Crystalline sheets of Ta0583. His[6]-tagged Ta0583 has a strong tendency for precipitation upon addition of glycerol. Negative stain electron microscopy revealed that the precipitate consists of crystalline sheets of Ta0583. (a) A low-resolution image of the Ta0583 sheets. (b) A raw image at higher magnification; (d) the corresponding Fourier filtered image. The power spectrum in (c) reveals a rectangular unit cell with dimensions of 51 Å and 122 Å. The crystalline arrays diffract to a resolution of 16.4 Å. The scale bar in (a) represents 2000 Å, and the scale bar in (b) represents 200 Å.

Figure 4.
Figure 4. Comparison of actin with prokaryotic homologs. The monomer structures of Ta0583, ParM,21 T. maritima MreB17 and mammalian actin5 (PDB codes 1mwm, 1jcf, and 1j6z) were superposed with Lsqman.40 The backbones are shown in ribbon representation. The color-coding of subdomains Ia to IIb is the same as in Figure 3. The ADP molecule bound to actin is shown in ball-and-stick representation.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2006, 358, 145-156) copyright 2006.

Figures were selected by the author.