Structure of holo-chaperonin studied with electron microscopy. Oligomeric cpn10 on top of two layers of cpn60 rings with two stripes each.
A structural model of holo-chaperonin, known as a protein-folding control protein comprising 60 kDa (cpn60) and 10 kDa polypeptides (cpn10), is proposed based on the electron microscopic images of holo-chaperonin from Thermus thermophilus and cpn60 from Paracoccus denitrificans. Isolated Paracoccus cpn60 shows very similar images to those of Escherichia coli tetradecameric cpn60, a seven-membered ring in the top view and a rectangular shape with four stripes in the side view. However, a small number of half-thick rectangles with two stripes are also seen which indicates that a single cpn60-heptamer ring has two stripes parallel to the plane of the ring. Thermus holo-chaperonin shows a bullet-like shape in the side view, and antibody against cpn10 binds only to the round side of the bullet. We conclude that a single cpn60-heptamer ring with two stripes stacks into two layers, and a cpn10 oligomer binds to one side of the layers.
Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan.
N
N
Ishii
H
H
Taguchi
M
M
Sumi
M
M
Yoshida
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D015153:Blotting, Western; D018833:Chaperonins; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010230:Paracoccus / Q000378:metabolism; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure; D013824:Thermus / Q000378:metabolism
D001426:Bacterial Proteins; D011506:Proteins; D018833:Chaperonins