7SOG image
Entry Detail
PDB ID:
7SOG
Keywords:
Title:
Thermostable actophorin
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2021-10-30
Release Date:
2022-04-20
Method Details:
Experimental Method:
Resolution:
1.74 Å
R-Value Free:
0.22
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Actophorin
Mutations:S2P, H21K, Q22K, T27I, M30L, A32D, S33D, H41K, K53L, S54A, R59N, Q71E, T81V, T99A, T101S, S104A, V110D, A122D, S130K
Chain IDs:A, B
Chain Length:135
Number of Molecules:2
Biological Source:Acanthamoeba castellanii
Ligand Molecules
Primary Citation
Structure and activity of a thermally stable mutant of Acanthamoeba actophorin.
Acta Crystallogr.,Sect.F 78 150 160 (2022)
PMID: 35400667 DOI: 10.1107/S2053230X22002448

Abstact

Actophorin, which was recently tested for crystallization under microgravity on the International Space Station, was subjected to mutagenesis to identify a construct with improved biophysical properties that were expected to improve the extent of diffraction. First, 20 mutations, including one C-terminal deletion of three residues, were introduced individually into actophorin, resulting in modest increases in thermal stability of between +0.5°C and +2.2°C. All but two of the stabilizing mutants increased both the rates of severing F-actin filaments and of spontaneous polymerization of pyrenyl G-actin in vitro. When the individual mutations were combined into a single actophorin variant, Acto-2, the overall thermal stability was 22°C higher than that of wild-type actophorin. When an inactivating S2P mutation in Acto-2 was restored, Acto-2/P2S was more stable by 20°C but was notably more active than the wild-type protein. The inactivating S2P mutation reaffirms the importance that Ser2 plays in the F-actin-severing reaction. The crystal structure of Acto-2 was solved to 1.7 Å resolution in a monoclinic space group, a first for actophorin. Surprisingly, despite the increase in thermal stability, the extended β-turn region, which is intimately involved in interactions with F-actin, is disordered in one copy of Acto-2 in the asymmetric unit. These observations emphasize the complex interplay among protein thermal stability, function and dynamics.

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Primary Citation of related structures