Abstract
Vaccinia virus (VACV) uses microtubules for export of virions to the cell surface and this process requires the viral protein F12. Here we show that F12 has structural similarity to kinesin light chain (KLC), a subunit of the kinesin-1 motor that binds cargo. F12 and KLC share similar size, pI, hydropathy and cargo-binding tetratricopeptide repeats (TPRs). Moreover, molecular modeling of F12 TPRs upon the crystal structure of KLC2 TPRs showed a striking conservation of structure. We also identified multiple TPRs in VACV proteins E2 and A36. Data presented demonstrate that F12 is critical for recruitment of kinesin-1 to virions and that a conserved tryptophan and aspartic acid (WD) motif, which is conserved in the kinesin-1-binding sequence (KBS) of the neuronal protein calsyntenin/alcadein and several other cellular kinesin-1 binding proteins, is essential for kinesin-1 recruitment and virion transport. In contrast, mutation of WD motifs in protein A36 revealed they were not required for kinesin-1 recruitment or IEV transport. This report of a viral KLC-like protein containing a KBS that is conserved in several cellular proteins advances our understanding of how VACV recruits the kinesin motor to virions, and exemplifies how viruses use molecular mimicry of cellular components to their advantage.
Highlights
Vaccinia virus (VACV) is a large DNA virus that replicates in the cytoplasm [1] and produces morphologically distinct virions that have different roles in virus dissemination [2,3]
We demonstrate that the VACV F12 protein has structural similarity with kinesin light chain (KLC) and facilitates viral transport using a kinesin binding sequence (KBS) that is conserved in several neuronal proteins
Like KLC, F12 is a cytosolic protein as shown by Triton X-114 partitioning (Figure S2) in agreement with a recent report [56], F12 lacks the heptad repeats near the N terminus of KLC for binding kinesin heavy chains (KHCs)
Summary
Vaccinia virus (VACV) is a large DNA virus that replicates in the cytoplasm [1] and produces morphologically distinct virions that have different roles in virus dissemination [2,3]. Virus replication occurs in cytoplasmic factories and starts with the formation of membrane crescents, composed of lipid and viral protein These extend into spherical or oval immature virions (IVs) containing the viral genome and core proteins [4,5]. The KLCs contain N-terminal heptad repeats, which interact with the central coiled stalk of the KHCs, followed by tetratricopeptide repeats (TPRs) that bind cargo [23]. Both KHCs and KLCs have been implicated in attaching kinesin-1 to cargo [24]. Mechanisms for cargo binding to, and release from, the KLC TPR are important aspects of cell biology [39,40,41]
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