Membrane proteins are of extraordinary importance for cell and organ function. In general, about one third of the genes in most currently sequenced species code for these proteins. However, it is not only the percentage of genes coding for membrane proteins which appears remarkable, the wide variety of functions fulfilled by membrane proteins are even more impressive:
- they generate action potentials and define the membrane potential;
- they are involved in nutrient import and in export of metabolic end-products across the plasma membrane;
- they transduce and induce signalling processes;
- they constitute the respiratory and photosynthetic electron transport chains;
- they influence cell shape, cell adhesion and cell motility;
- they are involved in anabolic and catabolic reactions with intermediates; and
- they are critical for ion and water homeostasis.
This list is, of course, not complete but it highlights why this group of proteins is present in virtually every membrane from pro- and eukaryotes. Accordingly, great progress has been made in the past in the molecular identification and functional characterisation of a wide number of these proteins.
The extraordinary importance of membrane proteins is exemplified by the growing research efforts on them and by the many Nobel prizes awarded to membrane researchers in recent years, e.g. Paul Boyer, John Walker and Jens Skou (1997), Günter Blobel (1999), Peter Agre and Roderick MacKinnon (2003), or Richard Axel and Linda Buck (2004). Therefore, it is not surprising that more than 1.2 x 106 scientific papers contain the term “membrane protein”, underlining the importance of this protein group.
In summary, research on membrane proteins and their implication for developmental processes and disease is fundamental, mandatory, and represent the cutting edge of corresponding research.