The Biology of Belief - Bruce H. Lipton [22]
And to be even more accurate, you should know that the amino acid necklace, which forms the “backbone” of the cells’ proteins, is far more malleable than a pop bead necklace, which falls apart when you bend it too much. The structure and behavior of the linked amino acids in the protein backbones better resemble that of a snake’s backbone, as shown below. (©Warren Jacobi/Corbis) The spine of a snake, made up of a large number of linked subunits, the vertebrae, is capable of coiling the snake into a wide variety of shapes, ranging from a straight rod to a knotted “ball.”
The flexible links (peptide bonds) between amino acids in a protein backbone enable each protein to adopt a variety of shapes. Through the rotation and flexion of their amino acid “vertebrae,” protein molecules resemble nano-snakes in their ability to writhe and squirm. There are two primary factors that determine the contour of a protein’s backbone and therefore its shape. One factor is the physical pattern defined by the sequence of differently shaped amino acids comprising the pop bead–like backbone.
Unlike uniform-shaped pop beads, each of the twenty amino acids comprising protein backbones has a unique shape (conformation). Consider the differences between the character of a “backbone” made from identically shaped pop beads and one assembled from the differently shaped pipe fittings illustrated above.
The second factor concerns the interaction of electromagnetic charges among the linked amino acids. Most amino acids have positive or negative charges, which act like magnets: like charges cause the molecules to repel one another, while opposite charges cause the molecules to attract each other. As shown on the following page, a protein’s flexible backbone spontaneously folds into a preferred shape when its amino acid subunits rotate and flex their bonds to balance the forces generated by their positive and negative charges.
The protein backbones shown in A and B have the exact same amino acid (pipe fitting) sequence but reveal radically different conformations. Variations in the backbone’s shape result from differential rotations at the junctions between adjacent fittings. Like pipe fittings, the protein’s differently shaped amino acids also rotate around their junctions (peptide bonds), allowing the backbone to wriggle like a snake. Proteins shape-shift though they will generally prefer two or three specific conformations. Which of the two conformations, A or B, would our hypothetical protein prefer? The answer is related to the fact that the two terminal amino acids (pipe fittings) have regions of negative charges. Since like charges repel each other, the farther apart they are, the more stable the conformation. Conformation A would be preferred because the negative charges are farther apart than they are in B.
The backbones of some protein molecules are so long that they require the assistance of special “helper” proteins called chaperones to aid in the folding process. Improperly folded proteins, like people with spinal defects, are unable to function optimally. Such aberrant proteins are marked for destruction by the cell; their backbone amino acids are disassembled and recycled in the synthesis of new proteins.
How Proteins Create Life
Living organisms are distinguished from nonliving entities by the fact that they move; they are animated. The energy driving their movements is harnessed to do the “work” that characterizes living systems, such as respiration, digestion, and muscle contraction. To understand the nature of life one must first understand how protein “machines” are empowered to move.
The final shape, or conformation (the technical term used by biologists), of a protein molecule reflects a balanced state among its electromagnetic charges. However, if the protein’s positive and negative charges are altered, the protein backbone will dynamically twist and adjust itself