Energy cost of biological accuracy and timekeeping

4 problems

• Does the cyanobacterial KaiABC clock run near minimal cost?

  Open

  Three proteins called KaiA, KaiB and KaiC keep a 24-hour rhythm in a test tube by burning ATP. The question is whether they spend close to the least energy that physics allows for their precision.

• Minimal dissipation for a given error rate and speed

  Partially resolved

  Kinetic proofreading, proposed by Hopfield in 1974, lets an enzyme reject wrong building blocks more than once by spending energy. The minimum energy needed for a given error rate at a given speed is not known in general.

• Do ribosomes operate at the speed-accuracy-cost optimum?

  Partially resolved

  The ribosome, the machine that builds proteins, could be more accurate if it slowed down or spent more energy. The question is whether its measured rates place it at the best possible balance.

• How T cells discriminate foreign from self antigens

  Contested

  Immune T cells must react to a few foreign protein fragments among many thousands of similar self fragments that bind only slightly less tightly. Simple proofreading cannot achieve both this sensitivity and this selectivity, so the actual mechanism is unknown.