Abstract
Spastin, an AAA ATPase mutated in the neurodegenerative disease hereditary spastic paraplegia, severs microtubules. Many other AAA proteins form ring-shaped hexamers and contain pore loops, which project into the ring's central cavity and act as ratchets that pull on target proteins, leading, in some cases, to conformational changes. We show that Spastin assembles into a hexamer and that loops within the central pore recognize C-terminal amino acids of tubulin. Key pore loop amino acids are required for severing, including one altered by a disease-associated mutation. We also show that Spastin contains a second microtubule binding domain that makes a distinct interaction with microtubules and is required for severing. Given that Spastin engages the MT in two places and that both interactions are required for severing, we propose that severing occurs by forces exerted on the C-terminal tail of tubulin, which results in a conformational change in tubulin, which releases it from the polymer.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism*
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Amino Acid Sequence
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Amino Acids / metabolism*
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Animals
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Axons / metabolism
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Axons / pathology
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COS Cells
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Chlorocebus aethiops
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Microtubules / metabolism*
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Microtubules / pathology
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Microtubules / ultrastructure
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Models, Molecular
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Molecular Sequence Data
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Mutation / genetics
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Neural Pathways / metabolism
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Neural Pathways / pathology
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Neural Pathways / physiopathology
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Protein Conformation
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Protein Structure, Tertiary / physiology
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Spastic Paraplegia, Hereditary / metabolism
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Spastic Paraplegia, Hereditary / pathology
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Spastic Paraplegia, Hereditary / physiopathology
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Spastin
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Tubulin / chemistry
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Tubulin / genetics
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Tubulin / metabolism*
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Wallerian Degeneration / metabolism
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Wallerian Degeneration / pathology
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Wallerian Degeneration / physiopathology
Substances
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Amino Acids
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Tubulin
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Adenosine Triphosphatases
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Spastin
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SPAST protein, human