Friday, June 21, 2013

Protein Fabricators

Biology textbooks summarize the flow of genetic information as follows: DNAà RNAà Protein. Our two previous posts dealt with the first two elements of this basic flowchart. Genetic inheritance begins with DNA. We did not always possess this knowledge. Arguments about the origin and flow of genetic information occurred even before the structure of the DNA molecule was discovered in 1953.

Protein had been suspected as the bearer of genetic information by many scientists in previous decades. The experiment of Avery, McCarty, and MacLeod in 1944 was reasonably conclusive that DNA was the hereditary material, but the biological world paid scant attention, occupied with other types of research. Knowledge of the trajectory of DNAà RNAà Protein has made its impact on science primarily within the lifetime of today’s baby-boomers.

If we are fascinated with knowledge of DNA’s encyclopedia of inheritance, or even with the wonder of the “messenger service” provided by mRNA and its counterparts, let us discuss our knowledge of protein fabrication as the final member of this fundamental biological trio. Perhaps it is the most fascinating member. A new term originated in 1997--proteomics--to describe the “large-scale study of proteins, particularly their structures and functions.” Knowledge of how the cells construct the proteins which comprise the structure and function of the bodies of living things is a fascinating prequel.

Imagine we were observers at a construction site, whether the building of our personal new residence or a skyscraper. Now envision a scenario where the builders do not merely fabricate the structure from previously prepared building materials such as wood, plastic, and metal already formed into shapes and sizes easily assembled. You must envision a building site where we observe the growth of the trees, learn about the manufacture of the plastics, and watch as the metal ores are refined.

Is this imaginary scenario unrealistic? Yes, it is. When we learn about the final step of protein formation in the cell, however, complexity of man-made building projects appears uncomplicated and simple by comparison. The mRNA leaves the nucleus of the cell with its coded directions for forming multiple proteins composed of just twenty amino acids. The mRNA will enter the protein manufacturing structures outside the nucleus, the ribosomes. These structures will link together the amino acids into unlimited numbers of chain structures.

Campbell and Reece in Biology, concerning the linkage of amino acids into chains, state, “The primary structure is like the order of letters in a very long word. If left to chance, there would be 20127 different ways of making a polypeptide chain 127 amino acids long. However, the precise primary structure of a protein is determined, not by the random linking of amino acids, but by inherited genetic information.” No more could we observe the processes of house-building or skyscraper-building crews and pronounce them the product of random chance than we could attribute the process of human body formation with its 100,000 or more different proteins--the correct ones--and deny the ubiquitous reality of divine intelligent design wherever we observe.

The long linear amino acid chains are manufactured and meticulously coiled and folded into specific three-dimensional shapes by the workhorse ribosomes. The biological principle of “form fits function” is a principle articulated in modern biology textbooks. The principle is thoroughly appropriate with respect to the folding of proteins. It applies to molecules, cells, tissues, organs, and complete organisms. “Form fits function” applies to every relationship between biological entities and their purpose, including the formation of proteins. Unique 3-D shapes endow the countless proteins comprising living things with a specific function.

This discussion merely scratched the outer surface of the flowchart topic DNAà RNAà Protein. Knowledge of the workings of the natural world is a good place to develop a rational apologetic for the reality of our omnipotent, omniscient, and thoroughly loving Heavenly Father.