The internal compartmentation of rat‐liver mitochondria: Tomographic study using the high‐voltage transmission electron microscope

Abstract

The three-dimensional organization of the internal compartments of conventionally fixed and embedded rat-liver mitochondria has been determined by tomographic reconstruction from tilt-series images collected on the Albany high-voltage electron microscope. The results indicate that the inner membranes of these organelles are predominantly tubular in the orthodox (expanded matrix) conformation, as previously suggested by scanning electron microscopy. In the condensed (contracted matrix) conformation, the intracristal space opens up into large irregularly shaped compartments which are connected to each other and to the external (intermembrane) space by tubes with approximately the same diameter (20 nm) as those observed in the orthodox state. These results raise several questions, in particular about the nature of the structural transitions that occur in the cristae during matrix expansion and contraction, and about the influence of inner-membrane shape on the diffusion of ions and metabolites between the intracristal and intermembrane compartments.

Topology of the Mitochondrial Inner Membrane: Dynamics and Bioenergetic Implications

“…Electron tomography of mitochondria from a wide variety of sources, both isolated and in situ, clearly indicates the deciencies of the old standard model for mitochondrial structure (8)(9)(10)(11)(12)(13). The cristal infoldings of the mitochondrial inner membrane are not baf e-like but instead are pleomorphic, usually connected through narrow tubular segments of varying length to the peripheral surface of the inner membrane and to one another.…”

“…More recently, highresolution scanning electron microscopy also has pointed to an internal structure very different from that postulated in the "baf e" model (6). However, the most convincing evidence against the standard model has been provided by a TEM technique that reconstructs the full 3D density of intracellular components, namely, high-voltage electron tomography (7,8).…”

Mitochondrial hepato-encephalopathy due to deficiency of QIL1/MIC13 (C19orf70), a MICOS complex subunit

“…1,2 The cristae are separated from the IBM by narrow tubular openings termed cristae junctions (CJs), which are thought to limit the dynamic distribution of the proteins along the IMM and partition the metabolite content of the intracristal and the intermembrane spaces. 3 The mechanisms underlying the lateral organization of the inner membrane into subdomains are not completely understood. Recently, however, a protein complex highly conserved from yeast to humans named 'mitochondrial contact site and cristae organizing system' (MICOS), was discovered and implicated in inner membrane structure.…”

The Role of Mitochondria in Syncytiotrophoblast Cells: Bioenergetics and Steroidogenesis

“…Although many types of mitochondrial cristae structure have been described (Munn, 1974), from recent electron microscopic tomography studies, the differences between typical mitochondria are now evident; e.g., liver (Mannella, 1994(Mannella, , 1997, neuronal (Perkins, 1997(Perkins, , 2001a, brown adipose tissue (Perkins et al, 1998), fungus (Nicastro et al, 2000;Perkins et al, 2001b), rods and cones (Perkins, 2003), and those from steroidogenic tissues, e.g., Leydig cells (Prince, 2002). In general, cristae from typical mitochondria are lamellar while in steroidogenic cells are tubular, vesicular, or tubulovesicular (Reichert et al, 2002).…”