Darwin's finches inside a living cell
On Thursday morning, November 24, 1859, a monumental text had hit the bookstores of London. It was Charles Darwin's study "On the origin of species" – the book that triggered a silent revolution in how we understand the origins of diversity among the living forms on our planet.
One example that Darwin used to show how forces of evolution shape anatomy of animal bodies was his study of tropical mockingbirds, finches, which he observed during his trip to Galapagos islands. Darwin found that closely related species of finches have highly diversified beaks, which shape and size were matching finches' dietary habits. For instance, Cactus finches had a slim and elongated beak that helped these birds to consume cactuses, whereas Ground finch had an enormously developed crushing bill that allowed them to use seeds in their diet. These observations, supported by studies of other numerous live and excavated species, eventually led Darwin to a discovery of three natural forces that cooperate to drive the evolution of all living species on Earth. Thus, Darwin found that (i) animals of one particular species are not immutable, and not precisely the same, but show random variations in anatomy, physilogy and behavior, (ii) some of these variations are inheritable, (iii) and if these inheritable variations help animals to strive through the process of natural selection – for instance, by helping find food or a partner for mating, – they lead to the origin of new living species with functionally distinct and specialized anatomy or behavior.
A hundred of years have passed from those revolutionary observations, and we humans had aquired another powerfull skill. By 1959, Max Perutz had established a method that allowed to decipher the molecular structure of the protein haemoglobin, which transports oxygen in the blood. Due to this method – known as the X-ray protein crystallography, – humanity could observe for the first time a complex and essential component of a living cell which size was about 1,000,000,000 smaller than that of a human body – the object not only invisible for a naked eye, but also elusive for the most powerful microscope of the time. This achievement have profoundly advanced our ability to observe nature: we have learnt how to see positions of individual atoms in molecules comprising living bodies!
From that moment, we were able to determine structures of nearly every vital part of a living cell. We revealed molecules that makes us breath, walk, think, learn and feel. Molecules that govern our behavior. Molecules that bind and transfer nutrients and drugs inside our bodies. Molecules that cause genetic disorders. Molecules that endow our body with its vital ability to sence and adapt to the environment.
Over the following decades, it gradually turned out that many individual components of a human cell – such as proteins, nucleic acids and their assemblies, – have their relatives in cells of bacteria, plants and fungi. And most strikingly, these relative molecules were found to be different in different species, and possibly underwent the same route of functional specialization as beaks of Galapagos finches. In other words, evolutionary changes – initially observed by exploring body parts of plants and animals with a naked eye – are also taking place deep inside our body when you look at it at 1,000,000,000 magnification!
One exciting challange we are facing today is to understand how changes in the architecture of the tiny building blocks of a living cell modify appearance, physiology and behaviour of living species. The problem is that – unlike beaks of mockingbirds, leave shape of plants, etc – many structural features of cellular proteins and nucleic acids do not have a known physiological functions. I therefore have established this website to provide a case study of one essential cellular component – the ribosome – a complex assembly of proteins and nucleic acids that accomplishes protein synthesis in a living cell.
Ribosomes are particularly interesting objects to study evolution of molecules comrising a living cell. They are present in every single cell on Earth, without exceptions; their structure has been determined for all major taxonomic groups of living species; and their shape, size and composition dramatically vary across species, suggesting that protein synthesis machinery is working in a highly specialized manner in different species. I therefore compare and contrast ribosome structure in different species in order to understand functional specialization of ribosomes across forms of life. Thus, like animals diversified their body parts to adapt to new environment, the molecules inside of our bodies have diversified their structure to enable unique aspects of metabolism and cell physiology.
What do these changes mean? Evolution is not an abstract term or history of the past, it is a process and the best predictor of what may happen in future or what we can do by means of engineering and synthetic biology.