INVESTIGADORES
GONZALEZ Daniel Hector
artículos
Título:
Biogenesis of mitochondrial c-type cytochromes
Autor/es:
GONZALEZ, DANIEL H.; NEUPERT, WALTER
Revista:
JOURNAL OF BIOENERGETICS AND BIOMEMBRANES
Editorial:
SPRINGER/PLENUM PUBLISHERS
Referencias:
Lugar: New York; Año: 1990 vol. 22 p. 753 - 768
ISSN:
0145-479X
Resumen:
Cytochromesc andc
1 are
essential components of the mitochondrial respiratory chain. In both
cytochromes the heme group is covalently linked to the polypeptide chain
via thioether bridges. The location of the two cytochromes is in the
intermembrane space; cytochromec is loosely attached to the surface of the inner mitochondrial membrane, whereas cytochromec
1 is firmly anchored to the inner membrane. Both cytochromec andc
1 are
encoded by nuclear genes, translated on cytoplasmic ribosomes, and are
transported into the mitochondria where they become covalently modified
and assembled. Despite the many similarities, the import pathways of
cytochromec andc
1 are drastically different. Cytochromec
1 is made
as a precursor with a complex bipartite presequence. In a first step the
precursor is directed across outer and inner membranes to the matrix
compartment of the mitochondria where cleavage of the first part of the
presequence takes place. In a following step the intermediate-size form
is redirected across the inner membrane; heme addition then occurs on
the surface of the inner membrane followed by the second processing
reaction. The import pathway of cytochromec is exceptional in practically all aspects, in comparison with the general import pathway into mitochondria. Cytochromec is synthesized as apocytochromec
without any additional sequence. It is translocated selectively across
the outer membrane. Addition of the heme group, catalyzed by cytochromec heme lyase, is a requirement for transport. In summary, cytochromec
1 import appears to follow a conservative pathway reflecting features of cytochromec
1 sorting in prokaryotic cells. In contrast, cytochromec has invented a rather unique pathway which is essentially non-conservative.