Cameras Film a Ring Protein Catching DNA Strands

Researchers in Japan have filmed a ring-shaped protein complex opening, closing and pulling two strands of DNA together at molecular scale.

The team at Kanazawa University and the National Institute of Genetics used high-speed atomic force microscopy to watch the Smc5/6 complex work on purified DNA. Their study was published in Nature Communications on November 4. [Scientists discover how a ring-shaped protein captures and brings together DNA strands — Kanazawa University / National Institute of Genetics release (PDF)] [Umeda et al., Submolecular video-imaging of the Smc5/6 complex topologically bound to DNA — Nature Communications (DOI)]

Smc5/6 is one of the protein machines that help maintain and repair genetic material. The images show it switching between two distinct shapes as its long arms open and close. In that motion it captures DNA, brings separate sections of it together and holds twisted sections in place, producing more tightly packed arrangements than the DNA had before. [Scientists discover how a ring-shaped protein captures and brings together DNA strands — Kanazawa University / National Institute of Genetics release (PDF)]

The work was led by Kenichi Umeda, Yumiko Kurokawa, Noriyuki Kodera and Yasuto Murayama, using protein purified from budding yeast. High-speed atomic force microscopy follows movements at the nanometre scale with an extremely fine probe, which is what makes a molecular process like this visible as a sequence rather than a single snapshot. [Scientists discover how a ring-shaped protein captures and brings together DNA strands — Kanazawa University / National Institute of Genetics release (PDF)] [Umeda et al., Submolecular video-imaging of the Smc5/6 complex topologically bound to DNA — Nature Communications (DOI)]

The caveats are printed in the release itself. The experiments ran on purified proteins and DNA in controlled laboratory conditions, outside living cells, so the images show molecular interactions directly without establishing every step of how the complete process runs inside a cell. The team also states the study is fundamental molecular biology and does not demonstrate a medical treatment or clinical application. [Scientists discover how a ring-shaped protein captures and brings together DNA strands — Kanazawa University / National Institute of Genetics release (PDF)]

What the footage settles is a mechanism question: how a complex known to matter for genome maintenance physically handles the material it maintains. The answer, now on camera, is that it grabs, aligns and compacts — and its shape changes do the gripping. [Scientists discover how a ring-shaped protein captures and brings together DNA strands — Kanazawa University / National Institute of Genetics release (PDF)]