Neck-Linker Length Dependence of Processive Kinesin-5 Motility

Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Journal of Molecular Biology (Impact Factor: 4.33). 07/2012; 423(2):159-68. DOI: 10.1016/j.jmb.2012.06.043
Source: PubMed

ABSTRACT Processive motility of individual molecules is essential for the function of many kinesin motors. Processivity for kinesins relies on communication between the two heads of a dimeric molecule, such that binding strictly alternates. The main communicating elements are believed to be the two neck linkers connecting the motors' stalks and heads. A proposed mechanism for coordination is the transmission of stress through the neck linkers. It is believed that the efficiency of gating depends on the length of the neck linker. Recent studies have presented support for a simple model in which the length of the neck linker directly controls the degree of processivity. Based on a previously published Kinesin-1/Kinesin-5 chimera, Eg5Kin, we have analyzed the motility of 12 motor constructs: we have varied the length of the neck linker in the range between 9 and 21 amino acids using the corresponding native Kinesin-5 sequence (Xenopus laevis Eg5). We found, surprisingly, that neither velocity nor force generation depended on neck-linker length. We also found that constructs with short neck linkers, down to 12 amino acids, were still highly processive, while processivity was lost at a length of 9 amino acids. Run lengths were maximal with neck linkers close to the native Kinesin-5 length and decreased beyond that length. This finding generally confirms the coordinating role of the neck linker for kinesin motility but challenges the simplest model postulating a motor-type-independent optimal length. Instead, our results suggest that different kinesins might be optimized for different neck-linker lengths.

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    • "prematurely binds ADP from the APO state , it will not be tightly bound to the MT when the first head hydrolyses ATP and detaches ( Valentine and Block , 2009 ) . Eg5 has a longer neck linker than kinesin - 1 , but studies differ as to whether Eg5 ' s longer neck linker may be responsible for its reduced processivity ( Shastry and Hancock , 2011 ; Duselder et al . , 2012 ) . Another possible explanation is that Eg5 remains MT - bound during processive stepping as long as it releases ADP from the ADP·Pi state , but if it releases Pi before ADP or binds ADP with its other head , it detaches . In this manner , Eg5 ' s mechanochemical properties may be the result of its unique kinetics , which certainly inv"
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