A NCMIR image of a mitochondrion reconstructed through electron tomography was featured on the cover of Nature Structural and Molecular Biology.

The image accompanied two reports on the discovery of a new subcellular component in the mitochondrial import machinery of the inner membrane. This protein, a cochaperone, is essential for transporting polypeptides into the matrix.

Pam16, the newly identified type of motor subunit required to promote a functional presequence translocase-associated protein import motor (PAM) reaction cycle, drives preprotein import into the matrix. Until the release of these studies, only four components of the machinery had been identified. Pam16 is the fifth.

The featured NCMIR image illustrates a model with the four known components in this machinery. The proteins facing the intermembrane space are yellow and the translocating preprotein is red (lower right). The larger image is a mitochondrion reconstructed from electron tomography. (Image courtesy of G.A. Perkins and T.G. Frey.)

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