A Common Evolutionary Origin for Mitochondria and Hydrogenosomes (Symbiosis/Organelle/Anaerobic Protist) ELIZABETH T
Proc. Natl. Acad. Sci. USA Vol. 93, pp. 9651-9656, September 1996 Evolution A common evolutionary origin for mitochondria and hydrogenosomes (symbiosis/organelle/anaerobic protist) ELIZABETH T. N. BuI*, PETER J. BRADLEYt, AND PATRICIA J. JOHNSONt#§ Departments of tMicrobiology and Immunology and *Anatomy and Cell Biology and tMolecular Biology Institute, University of California, Los Angeles, CA 90095 Communicated by Elizabeth F. Neufeld, University of California, Los Angeles, CA, June 21, 1996 (received for review May 12, 1996) ABSTRACT Trichomonads are among the earliest eu- hydrogenase, a marker enzyme of the hydrogenosome, nor do karyotes to diverge from the main line of eukaryotic descent. they produce molecular hydrogen. Pyruvate/ferredoxin oxi- Keeping with their ancient nature, these facultative anaerobic doreductase and hydrogenase are, in contrast, commonly protists lack two "hallmark" organelles found in most eu- found in anaerobic bacteria. Like mitochondria, hydrogeno- karyotes: mitochondria and peroxisomes. Trichomonads do, somes are bounded by a double membrane (15); however, the however, contain an unusual organelle involved in carbohy- inner membrane neither forms cristae nor contains detectable drate metabolism called the hydrogenosome. Like mitochon- cytochromes or cardiolipin as found in mitochondria (16, 17). dria, hydrogenosomes are double-membrane bounded or- Also, hydrogenosomes do not appear to contain FOF1 ATPase ganelles that produce ATP using pyruvate as the primary activity (18). On the other hand, ATP is produced in hydro- substrate. Hydrogenosomes are, however, markedly different genosomes via catalysis by succinyl CoA synthetase (19, 20), a from mitochondria as they lack DNA, cytochromes and the Krebs cycle enzyme that catalyzes the same reaction in hy- citric acid cycle.
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