All living things depend on proteins. Yet I sometimes wonder just how many people pause to consider just how amazing proteins are. Consider your own body. If you dig deep enough, it’s often as if a major organ system is centered around the function of a protein or small subset of proteins. Your muscles? Think of actin and myosin, the contractile proteins. Your brain and nerves? Think of the membrane receptors and channels that generate and transmit electrical signals. Your blood? Think of the hemoglobin that transports oxygen. Your digestive system? Think of the enzymes that break down all the food molecules (which, of course, include proteins). Your bones and joints? Think of collagen that binds things together. Your skin and hair? Think of that tough protein, keratin. Your glands? Think of hormones and the receptors that detect them. Your immune system? Think of the antibodies that guard your body.
See proteins as design material and suddenly you are struck by their immense versatility, as if they represent the ultimate, all-purpose substance for generating function.
They can generate light, detect light, or use light to generate ion gradients and chemical energy. They can act as a signal or detect a signal. They can impart movement and function as motors. You can use them to bind things together and to unbind things. They can be used to catalyze thousands of chemical reactions, transport tiny or bulky molecules, transmit signals across great distances, and/or proofread. They can exist as everything from a simple fiber to a complex, sophisticated molecular machine. They can function alone or as part of a circuit. Combine them with lipids, and you have a controllable barrier, perfect for compartmentalization. Combine them with DNA and you have a chromosome that can be regulated and packaged. Combine them with RNA and you have machines that can make proteins and perfectly splice genes. You can use them to evolve things, as the deeply influential processes of gene duplication, recombination, and horizontal gene transfer are dependent on, you guessed it, proteins. You can even use proteins to form the hard turtle shell, soft bunny fur, and the flight feathers of a duck.
One then wonders if there exists a more versatile design material in the entire Universe. But it gets even better. At the heart of all this mind-numbing functionality and versatility that has served Life for billions of years is the very same manufacturing process. Now that’s a design material: one manufacturing process coupled to thousands upon thousands of functions.
This all raises some interesting questions. For example, without proteins, and their manufacturing process, what becomes of the blind watchmaker? Without proteins, and the latent functions contained within, might not the blind watchmaker exist as the impotent, crippled, blind watchmaker with no one to notice its existence? If so, how much credit does the blind watchmaker really deserve?
Of course, if it all began, as they say, by coopting certain amino acids to act as catalytic groups, or fortuitously latching on to small peptides to function as cross-linkers, it was perhaps the Most Lucky Event of all that such humble material contained within it the latent potential to turn the blind watchmaker into a rather impressive designer-mimic.