Abstract
The biological clock of cyanobacteria is composed of three proteins, KaiA, KaiB, and KaiC. The KaiB-KaiC binding brings the slowness into the system, which is essential for the long period of the circadian rhythm. However, there is no consensus as to the origin of the slowness due to the pre-binding conformational transition of either KaiB or KaiC. In this study, we propose a simple KaiB-KaiC binding scheme in a hexameric form with an attractive interaction between adjacent bound KaiB monomers, which is independent of KaiB’s conformational change. We then show that the present scheme can explain several important experimental results on the binding, including that used as evidence for the slow conformational transition of KaiB. The present result thus indicates that the slowness arises from KaiC rather than KaiB.
Highlights
The biological clock of cyanobacteria is composed of three proteins, KaiA, KaiB, and KaiC
This study has further shown that both the initial rapid and the subsequent slow bindings can be explained in a unified manner by assuming a conformational-selection binding scheme, i.e. a slow pre-binding conformational transition of KaiB dominates the binding
In the present scheme, the initial rapid and the subsequent slow bindings correspond to the bindings from C6B0 to C6B1 and from C6B1 to the other larger KaiB-KaiC complexes C6Bn (n > 1), respectively
Summary
The biological clock of cyanobacteria is composed of three proteins, KaiA, KaiB, and KaiC. We propose an alternative binding scheme that can explain both the initial rapid and the subsequent slow KaiB-KaiC bindings observed in Chang’s experiment[21].
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