Review – Power, Sex, Suicide: Mitochondria and the Meaning of Life – Nick Lane
Stuart Ferguson, Dept. of Biochemistry, University of Oxford
There was a time when students read, rather than studied, subjects at universities. The idea was that there was not a strict syllabus laid down by course handbooks, but rather students should also read around their subject in whatever directions they fancied. Nick Lane’s book contains exactly that sort of material which students of biological subjects, and for that matter their teachers, ought to find time to read. Why? Because it offers a thought-provoking synthesis of a number of features of contemporary mitochondrial biology and the intimately-related issue of why evolution of the eukaryotic cell was connected to the appearance of mitochondria.
There has, of course, been a renaissance of interest in mitochondria during the last ten years, with the consequence that mitochondria are no longer seen as being only involved in energy transduction. The ‘expansion’ of mitochondrial roles has not only provided much of the material for Nick Lane’s book, but also stimulated the special issue (June 2005) of the Biochemist that was devoted to mitochondria.
Mitochondrial biology must include energy transduction, and the mechanism and importance of this process is discussed. Indeed Lane argues that this topic deserves more attention than it receives. I recall that Horace Judson in the Eighth Day of Creation quotes Francis Crick as saying around 1960, “It is the information flow that counts, the energy flow can be left to take care of itself.” This view is still common today, but a principal thesis of this book is that much more of biology flows from the process of electron transport-linked ATP synthesis than most scientists realise. For example, it is argued that exclusive maternal inheritance of mitochondrial DNA is obligatory because of the need to assemble a fully functional energy transduction apparatus from mitochondrial and nuclear genes; it is preferable to avoid possible sequence variation in the mitochondrially-encoded respiratory proteins which would occur if both paternal and maternal inheritance occurred.
The ‘power’ aspect of the book comes first, and the development of Mitchell’s chemiosomotic mechanism for oxidative phosphorylation is described. Subsequently, it is argued that a proton-translocating ATP synthase, complex though this machine is, came early in evolution. The hydrogen hypothesis for evolution of a eukaryotic cell, that is the ‘collaboration’ of a methane-generating bacterium, which needed hydrogen, with a metabolically more versatile bacterium that could amongst other things generate hydrogen from sugars, is supported (later in the book, one could be forgiven for assuming that it is an established fact). The text proceeds on to discussion about why a eukaryotic cell could not operate its oxidative phosphorylation system on the plasma membrane. This is linked to issues of cell size and why bacterial evolution can be argued to have come to an end in this respect of size and complexity.
We are invited to think about why some mitochondrially-coded proteins are retained even in humans. The idea that retention of mitochondrially-encoded subunits of key components of the electron transport chain provides a mechanism for feeding information to the nucleus about requirement for increase or decrease in rates of synthesis of electron transport chain proteins is enthusiastically advocated. Later this leads into a discussion of why sex is necessary; all is very thought-provoking. Mitochondria are implicated in death, whether as a consequence of suicide or ageing. Much play is made of the rate of production of reactive species of oxygen, ie superoxide as a side-product, by the respiratory chain. Whereas the idea that oxygen radicals, produced as side-products of the mitochondrial respiratory chain, may contribute to progressive cell damage has been around for 30 years or more, the hot topic in mitochondrial biology is apoptosis. Nick Lane outlines how the ‘oxygen radicals drive cell ageing’ argument does not hold together quite as neatly as was once thought. He assembles data on lifespan and metabolic rate for analysis of this topic. Intriguing arguments are made throughout. The connection of the oxidative phosphorylation apparatus to apoptosis (suicide) is presented in an interesting way.
I am glad that I read this book; it made me think. But this book would be very hard-going for someone with no knowledge of any aspect of university-level biology. Although presented as a popular science book, I fear it is not even if the very articulate writing style makes the going as easy as it could be. One can argue that a popular book should tell a story of more or less-confirmed science. Nick Lane’s contribution is more than that because he is discussing, and in some case supporting, ideas that are not confirmed. He has brought together an enormous amount of material, obviously based on very extensive reading, in this book. Thus this is really a book for biochemists/biologists. Cambridge Part III Biochemists were asked in their 2006 examination, “What dictates the size of a bacterium?” Reading Power, Sex and Suicide would have given them a good start; reading around the subject is still useful!
I am happy to recommend wholeheartedly Nick Lane’s book to anyone who is interested in central issues in contemporary biology. He certainly demonstrates that mitochondria are more than ATP-producers, but nevertheless that their oxidative phosphorylation apparatus deserves plenty of attention. It seems that the energy flow cannot be left to take care of itself.