Thinking proteins

Proteins you think. About award Nobel Prize for Medicine 1994

Author: Mariano Artigas
Published in: Aceprensa, 1/95
date of on-line publication : 11 January 1995

On 11 October 1994, the press reported the award of the award Nobel Prize in Medicine to Professors Alfred G. Gilman and Martin Rodbell for "the finding of G-proteins and their role in signal transmission in cells". This is a new breakthrough in molecular biology, which sample provides ever greater detail on how life works and new instructions food for thought about nature.

Science, Philosophy and religion respond to different perspectives, and it is dangerous to mix them up. But that does not mean that they have nothing to do with each other. Science provides an ever more detailed knowledge of nature and thus broadens the basis for philosophical and religious reflection.

Today, this is especially true of molecular biology, which is progressing at an accelerated pace. Some think that this is a new triumph of reductionism, because it allows us to understand how life works through physical and chemical processes, without appealing to entelechies, souls or vital principles. However, the microphysical world we are discovering is so fantastic that it is difficult not to wonder about its ultimate explanation, beyond what science can discover.

Cells and proteins

Of course, G-proteins are proteins, and nothing more than proteins. They consist of amino acids linked together by chemical bonds called peptide bonds. At final, they are large groups of atoms arranged in long chains that fold in characteristic patterns. They play important roles in the body: for example, hormones are involved in the regulation of metabolic processes, and enzymes act as catalysts for reactions in the body.

There are more than 10 trillion cells in the human body, divided into more than 250 cell types (nerve, blood, muscle, etc.). The cells are very small: it is estimated that a cube with an edge of 2.5 centimetres would contain about one billion cells of subject half. However, each cell is a miniature marvel: it contains in its nucleus all the information Genetics, and lives, so to speak, its own life: it receives substances from the outside, transforms them to obtain energy, throws out waste, manufactures the components the organism needs and exports them to the right place, reproduces itself by processes in which genetic material is duplicated and divided. The functioning of a single cell is enormously sophisticated.

Cells depend on each other for their existence and function. This is where a whole set of processes come into play, whereby cells act in a very specific way. They need to "know" what kinds of molecules are around them to let them in or to block them. They need to "know" what to do with incoming material. They also need to "know" the state of the organism, in order to act accordingly. It is a fascinating world that works on the basis of "information". And this is where the G-proteins play an important role.

G proteins

To get an idea of the nature and function of these proteins, we can help ourselves to a article written by one of the scientists who has just been awarded the award Nobel Prize for his programs of study on them *(1). G-proteins, in a nutshell, "are multifaceted molecules that, housed on the inner side of the cell membrane, coordinate cellular responses to numerous signals from the outside".

This article reminds us that in order for us to act and simply exist, the cells of our body must communicate with each other, and that this speech is done through chemical messengers. But few messengers need to penetrate cells: "most get the information to its destination via intermediaries. On the surface of the target cell there are proteins that serve as specific receptors: binding to them becomes a command. The receptors then "transmit the information in turn to a series of intracellular emissaries, which finally pass it on to the final executors".

Many of the extracellular messengers that have been discovered rely on G-proteins "to direct the flow of signals from the receptor to the rest of the cell". After recalling that G-proteins are so named because they bind guanine nucleotides, and that their function was discovered in the late 1970s, our award Nobel writes: "We continue to be fascinated by their abilities and the central role they play in a wide variety of cellular functions, which seem to be expanding every day".


It is interesting to note that scientists are still in awe of nature. They even, as we have just seen, speak of fascination. Why?

At first glance, it seems that advances in science rather eliminate admiration. One admires something when one does not know how it works, but if one discovers its mechanisms, there seems to be no more room for admiration. However, it is possible to see things differently. Indeed, if the mechanisms that are discovered are very sophisticated, it is logical to be surprised that nature, by itself and acting "blindly", is able to perform such subtle and complex operations at the same time.

This is what happens with G-proteins. When describing their activity, scientists speak of information, orders, messengers, emissaries, executors, coordinators, speech. All this would be nothing special if they were people. But they are chemical entities. We can go even further into this strange world by looking at other statements in the article guide .

The wonders of a routine world

In the late 1950s, the processes of cell signalling began to be understood. "We now know that a wide variety of cellular receptors echo the instructions of hormones and other extracellular "first messengers" by exciting one or another G-protein. Attached to the inner surface of the cell membrane, these proteins in turn act on intermediates also attached to the cell membrane, which are called effectors. Often, the effector is an enzyme that converts an inactive precursor molecule into an active second messenger, which diffuses through the cytoplasm and can then carry the signal beyond the boundaries of the membrane. The second messenger triggers a cascade of molecular reactions that results in a functional change in the cell; for example, it starts secreting a certain hormone, or releasing glucose, into the environment.

We are dealing with a world in which signals and instructions are transmitted through messengers that take over from one another. Of course, first and second messengers, as well as proteins and effectors, are not spirits or ghosts: they are physico-chemical entities. But they act in a way that we could simply call intelligent, if we consider that we are dealing with very specific and coordinated processes by which the basic functions of organisms exist. Of course, we will not find anyone directing the traffic or indicating what should be done at any given moment.

The list of discoveries is continually expanding. It is now known that G-proteins do " official document as switches and timers, determining when and for how long the pathways of speech open or close". Of course, they don't think, nor do they have clocks, nor have they studied Chemistry or biology. Moreover, "G proteins also amplify signals. For example, in the highly efficient visual system, one rhodopsin molecule almost simultaneously activates more than 500 transducin molecules". This is what is called polyvalence and efficiency! We can console ourselves when we are told that there are still many enigmas to be solved, but, if we think about it, this means that our current knowledge is only a part of the wonders that make the functioning of our organism possible.

A language problem?

One might think that, after all, the world of molecular biology is no different from any other area of the physical world, and that the employment of terms referring to information, instructions, and the like, only responds to the need to somehow explain processes that have nothing mysterious about them. But, in any case, it is striking that, when trying to explain their discoveries, scientists are compelled by the need to use a language full of meanings reminiscent of intelligent actions.

It is a double layer that separates the cell from its environment and, at the same time, makes possible the entrance and the exit of Materials, as well as the speech with other cells. Speaking of it, we are told: "the cell membrane is undoubtedly a highly complex control panel, receiving a variety of signals, assessing their relative strength and transmitting them to second messengers that will ensure the cell's appropriate reaction to a changing environment". And also: "the cell membrane is a kind of switchboard that can mix different signals, or redirect similar signals along different pathways, depending on the needs of the cell".

The processes thus develop according to the needs of the cell. It would seem that, at last, we find here something similar to the famous Marxist slogan: "from each according to his possibilities, to each according to his needs". Only, in this case, nature does it on its own. No doubt all this is partly in the language we ourselves (in this case, scientists) use, and perhaps it could be expressed in another language. But what is meant will not change. Not everything depends on language.

Revolutions, victims and victors

result Nowadays it is often repeated that there is no reason to wonder, because the wonders that science discovers are the result of a very long evolutionary process in which many competitors have competed and, logically, only the winners have survived. In other words: nature would have tried many other combinations, but only those with certain capabilities have survived.

This explanation may have some merit. It is not absurd or anti-scientific. What is not so clear is that it explains everything. Even if it is true that many results have been produced and only some of them have survived, how did these survivors come to be produced, is it not surprising that, even if by fits and starts, organisms have been produced whose functioning includes a multitude of very specific processes, coordinated with each other, which we are only now beginning to know after several centuries of scientific progress?

Evolution is a respectable scientific theory. To be sure, it contains conundrums, but this is true of all scientific theories: any progress on knowledge raises new problems. The pitfalls begin when it is claimed that evolution explains everything. Then, what was once a respectable scientific theory starts to become a myth. It is a myth built on a scientific basis, but it is still a myth.

Of course, it is not a question of fill in science "from outside" in its own domain. What is to be discovered about evolution in the scientific domain can only be discovered by science. It is simply to note that the scientific perspective does not exhaust reality and what we can ask and answer about it.

The power and wisdom of nature

At the end of article, our Nobel laureate award gives a glimpse into the future: "Eventually, a complete map of the plasma membrane will be compiled for each of the thousands of cell types in the human organism. In each case, it will be known how the dozens of different receptors, G proteins and effectors relate to each other. And it will be possible to predict how cells will react in response to any combination of signals. Half jokingly, someone has said that this would be to those working on the development of new drugs what it would be to a thief to receive the complete outline of a bank's alarm system".

It seems likely that more and more progress will be made in the direction indicated by these predictions. Let us hope so: why not even think that we will succeed in surpassing nature in this area, as we have already done in so many others?

The curious thing is that all our progress is based on the potentialities that nature possesses. As Bacon said, when modern science was still in its infancy: "To overcome nature we must obey it". We can use the resources that nature provides us with, but we cannot create them at our whim. And it is also curious that nature has achieved results on its own that, in many respects, still far surpass us.

Nature manifests a power and a wisdom which, as science progresses, we know in greater detail. In this sense, new discoveries do not suppress wonder at nature, but, on the contrary, increase it. And, unless we are prepared to admit a kind of pantheism that explains nothing, contemplation of the power and wisdom of nature leads hand in hand to the affirmation of a God staff creator who, although shrouded in mystery because he completely transcends the level of creatures, enables us to understand the grandeur of creation.

Of course, I believe in God long before I knew anything about G-proteins. It seems to me, moreover, that few people, if any, will come to affirm the existence of God by reflecting on G-proteins. The current advances in molecular biology are a very propitious area for such reflection. It is not a question of filling the gaps of our ignorance with religion; on the contrary, it is the progress of knowledge that invites deep reflection.

How would we see nature if we could look at it, with our own eyes, as it is described to us by today's science? We would see a fantastic micro-world, which surpasses many science-fiction imaginations. This world has existed for millions of years, is part of our own being, and invites us to a reflection that can be extremely enriching.

The implications of scientific progress

Science provides knowledge that greatly enriches our ideas about nature. It takes a different perspective from Philosophy and religion; but it is not opposed to them: the three perspectives complement each other. Reality has different dimensions, and a single perspective cannot encompass them all.

Under these conditions, the danger is to reduce reality to what we can know through only one of these perspectives. In former times, there may have been a danger that Philosophy or religion would go beyond their proper terrain. Nowadays, because of the enormous prestige of science, the danger is often to attribute the monopoly of knowledge to science. This monopoly is no longer science, because true science sticks rigorously to what it can achieve through its methods, and does not meddle with what falls outside its boundaries.

To avoid such a monopoly, it is enough to reflect on the implications of scientific progress. The more scientific knowledge spreads, as in the current case of molecular biology, the more astonishing the coordination and organisation of natural entities and processes becomes. It is not difficult to see that the scientific perspective is called upon to complement philosophical reflection and religion, and that this complementarity is also enriching for science, because it allows us to understand the meaning of its progress.

  1. This is article G Proteins, by Maurine E. Linder and Alfred G. Gilman, published in Research and Science, no. 192, September 1992, pp. 20-28. The italics in the quotations are my own: I use them to highlight words that relate to the transmission of information.