The Open Protein Structure Annotation Network
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    Table of contents
    1. 1. Protein Summary
    2. 2. Ligand Summary

    Title Prokaryotic origin of the actin cytoskeleton. Nature 413 39-44 2001
    Site OTHER
    PDB Id 1jce Target Id PDB1JCE
    Molecular Characteristics
    Source Thermotoga maritima
    Alias Ids TPS20022, TM0588 Molecular Weight 36751.64 Da.
    Residues 344 Isoelectric Point 5.97
    Sequence mlrkdigidlgtantlvflrgkgivvnepsviaidsttgeilkvgleaknmigktpatikairpmrdgvi adytvalvmlryfinkakggmnlfkprvvigvpigitdverraildagleagaskvflieepmaaaigs nlnveepsgnmvvdigggttevavislgsivtwesiriagdemdeaivqyvretyrvaigertaervki eignvfpskendelettvsgidlstglprkltlkggevrealrsvvvaivesvrttlektppelvsdii ergifltgggsllrgldtllqketgisvirseepltavakgagmvldkvnilkklqgaggshhhhhh
      BLAST   FFAS

    Structure Determination
    Method XRAY Chains 1
    Resolution (Å) 2.10 Rfree 0.2336000
    Matthews' coefficent 2.81 Rfactor 0.1973000
    Waters 266 Solvent Content 56.24

    Ligand Information



    Protein Summary

    The TM0588 (MreB) gene of Thermotoga maritima encodes a protein with sequence similarity to the actin superfamily. The crystal structure of MreB (1) reveals that MreB has the closest structural similarity to actin among all members of the actin family (Fig. 1). This relation is further supported by studies of MreB filament architecture and suggests that MreB may act as an actin homologue in bacteria.

    The MreB crystal structure comprises two domains (I, II) with a nucleotide-binding site formed in the interdomain cleft (Fig. 1). Subdomains IA and IIA share a common fold with a β-sheet surrounded by α-helices. Subdomains IB and IIB are more diverse but share the same topology as actin. The active-site residues involved in nucleotide and divalent cation binding in MreB are mostly similar with residues in the actin structure, and can be superimposed.



    Figure 1. Structural superposition of actin (PDB id: 1atn, in blue) and MreB (PDB id: 1jce, in gray). Both proteins share the same topology, four-domain architecture (subdomains IA to IIB in MreB, corresponding to subdomains 1-4 in actin) and most of the residues involved in ATP and magnesium binding.

    MreB has been implicated in determining cell shape in bacteria (1), suggesting that in addition to structure, MreB could also share a functional similarity with actin. This hypothesis is further supported by the observation of the protofilament architecture of MreB, as seen in both electron microscopy and crystal packing studies (1). The MreB protofilament has a spacing of 51 Å (1) which is comparable to the 55 Å repeat observed in filamentous actin (2). Since the structure determination of MreB, further experiments have shown that MreB shares other actin properties, such as treadmilling (3) and a role in chromosome segregation (4).

    Ligand Summary




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