Structure of crenactin, an archaeal actin homologue active at 90°C

• Published in: Acta crystallographica. Section D, Biological crystallography. Biological crystallography., 2014-02, Vol.70 (2), p.492-500
• Main Authors: Lindås, Ann-Christin, Chruszcz, Maksymilian, Bernander, Rolf, Valegård, Karin
• Format: Article
• Language: English
• Subjects: actin family; Actins - chemistry; Actins - genetics; Amino Acid Sequence; Archaeal Proteins - chemistry; Archaeal Proteins - genetics; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; crenactin; Crystallography, X-Ray; Cytoskeletal Proteins - chemistry; Cytoskeletal Proteins - genetics; Escherichia coli - genetics; Escherichia coli - metabolism; Evolution, Molecular; Hot Temperature; Models, Molecular; Molecular Sequence Data; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; Pyrobaculum - chemistry; Pyrobaculum - metabolism; Pyrobaculum calidifontis; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Saccharomyces cerevisiae - chemistry; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Sequence Alignment; Sequence Homology, Amino Acid; Thermotoga maritima - chemistry; Thermotoga maritima - metabolism
• ISSN: 1399-0047; 0907-4449; 1399-0047
• DOI: 10.1107/S1399004714000935

The crystal structure of the archaeal actin, crenactin, from the rod‐shaped hyperthermophilic (optimal growth at 90°C) crenarchaeon Pyrobaculum calidifontis is reported at 3.35 Å resolution. Despite low amino‐acid sequence identity, the three‐dimensional structure of the protein monomer is highly similar to those of eukaryotic actin and the bacterial MreB protein. Crenactin‐specific features are also evident, as well as elements that are shared between crenactin and eukaryotic actin but are not found in MreB. In the crystal, crenactin monomers form right‐handed helices, demonstrating that the protein is capable of forming filament‐like structures. Monomer interactions in the helix, as well as interactions between crenactin and ADP in the nucleotide‐binding pocket, are resolved at the atomic level and compared with those of actin and MreB. The results provide insights into the structural and functional properties of a heat‐stable archaeal actin and contribute to the understanding of the evolution of actin‐family proteins in the three domains of life.