Biochemistry

Előszó

This is a wonderful time in biochemistry. Recombinant DNA technol-ogy, protein chemistry, and structural biology have come together to reveal the molecular mechanisms of fundamental biological processes. Many of our dreams of only a few years ago have been fulfilled. One of the fruits of this continuing harvest is a deeper understanding of protein form and function. We now see that proteins are highly sophisticated molecular machines that process energy, matter, and information. Their beautiful molecular ballet is coming into view. Indeed, we can even see the steps taken by a single molecular motor and the flow of ions through a single membrane channel.
These profound advances compel a change in how biochemistry is taught. I have expanded Part II, Proteins: Conformation, Dynamics, and Function, to bring our new understanding of proteins into the core of biochemistry. Membrane channels and pumps, signal transduction cas-cades, antibodies and T-cell receptors, and molecular motors are now presented in Part II rather than in a separate section at the end of the book. The proteins considered in these chapters reveal much about fundamental processes such as free-energy conversion, signal amplification, and molecular recognition. An understanding of proteins as energy-transforming and information-processing devices enriches the study of metabolism. Oxidative phosphorylation and photosynthesis, for example, are more readily understood and appreciated if the proton-pumping mechanism of bacteriorhodopsin is considered first. Likewise, the hor-monal control of metabolism is easier to comprehend if G-protein and tyrosine-kinase cascades are presented first. Another noteworthy change is the new chapter on protein folding and design, an exciting area of inquiry that has broad import.
In 1962, the structures of only two proteins—myoglobin and hemo-globin—were known at atomic resolution. I was fortunate to see them at close rangé while I was a postdoctoral fellow at the Medical Research Council Laboratory of Molecular Biology in Cambridge, England. Max Perutz, John Kendrew, and the young crystallographers in the laboratory instilled in me a deep appreciation of molecular architecture and its im-portance in understanding the molecular basis of life. Now, three decades later, we see the fruition of structural biology. X-ray crystallography, joined by electron crystallography and nuclear magnetic resonance spec-troscopy, have revealed the structures of hundreds of proteins. This wealth of structural information has illuminated and enriched our understanding of how proteins function as enzymes, transporters, motors, signal transducers, and gene regulators. Recurring structural modules have come into view, bringing insight into how proteins evolved. Structural Vissza