Proteins Made by Design, Part 3 (of 3)

Proteins Made by Design, Part 3 (of 3)

New Insight about Biochemical Quality Control Adds to the Case for Intelligent Design

Several years ago a famous ad campaign for one of the big three automakers announced their commitment to the principle that “quality is job 1.” As I discussed last week, quality control appears to be “job 1” for many of the key biochemical process that take place in the cell.

And there is good reason for it. These activities ensure that biochemical products like proteins are manufactured properly. If not, the cell couldn’t survive long. In The Cell’s Design I talk about how the quality control operations of the cell suggest that life’s chemistry stems from the work of an Intelligent Agent.

Last week I pointed out that some of the most critical and sophisticated steps in any manufacturing operation are the quality control checks. Deliberately incorporated into the procedure, these tasks remove defective materials from the assembly sequence and make certain that no substandard finished product reaches the consumer’s hands.

Quality control measures intervene throughout a manufacturing process. Procedures that simply evaluate and reject out-of-specification finished products at the end of production processes are costly and inefficient. The best quality assurance checks step in at points where mistakes are most likely to occur or are the most costly.

Placing quality control checks at critical points in the production process yields manufacturing efficiency by removing a defective product near the point it occurs in the manufacturing sequence. This prevents the waste of resources and time. If not for immediate intervention, faulty materials accidentally generated in the midst of the manufacturing process will be carried through to the assembly line’s end, only to be discarded.

Most of the cell’s quality control processes adhere to these principles. Still, as with any manufacturing operation, defective biochemical products can still be produced, even with efficient checks in place. Because of this eventuality, a quality control step is still needed at the end of the process to reject defective products. And the biochemical processes are no exception.

Recent work by a team of biochemists has uncovered another quality control operation in the bacterium Escherichia coli. This quality assurance measure works on defective proteins that have somehow made it all the way through the production process without being detected. It occurs at the end of the manufacturing process and represents the final safeguard in protein synthesis.

This step is mediated by heat shock proteins. These large protein complexes help protect the cell’s proteins from stress caused by elevated temperatures. When temperatures rise, proteins unfold and adopt nonnative structures. Since protein structure is critical for protein function, elevated temperatures will disable proteins, putting the cell in a precarious position. Heat shock proteins bind to proteins, preventing them from unfolding, and thereby helping them maintain their native, functional state. Heat shock proteins also serve as chaperones that help other proteins fold into their final three dimensional shape after being made at the ribosome.

It appears as if heat shock proteins moonlight as quality control inspectors. This is a clever arrangement. Because heat shock proteins help other proteins fold and maintain stressed proteins in their native state, they can also “force” improperly made proteins into a near-native state, enough so that they can function. On the other hand, if damaged proteins are beyond “repair,” the heat shock proteins send them off for destruction. Instead of simply discarding defective materials, using heat shock proteins as the final quality assurance step provides one more opportunity to make use of defunct proteins. This protocol prevents unnecessary waste of precious cellular resources.

The newly discovered use of heat shock proteins bears resemblance to the strategy used in many man-made manufacturing operations. If a defective product is identified by quality control procedures, whenever possible, attempts are made to rework it before it is discarded, ensuring manufacturing efficiency.

Biochemical quality assurance further highlights the remarkable ingenuity that defines the cell’s chemistry and reinforces the conclusion that life has a supernatural basis. Effective and efficient quality control procedures don’t just happen. Rather, an intentional foresight characterizes them. Sound quality check systems require careful planning, and a detailed understanding of the manufacturing process, the product, and the way in which it will be used. All of these features are evident in the quality control activities in the cell, as this new discovery illustrates.

Part 1 | Part 2 | Part 3