The motor domain structure of dynein was worked out through looking at crystals of the wild type (WT) as well as the truncated mutant version, ΔMTBD. ΔMTBD differs from the WT by lacking a MTBD at the tip of its stalk, but still maintaining an ATPase activity close to that of WT, at around 111 molecules hydrolysed per second. Using three heavy-atom derivatives, the structure of ΔMTBD was solved, which serves as a molecular replacement search base to solve the structure of WT.
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| structure comparison: 3VKH - wild type (left), 3VKG - ΔMTBD (right) |
The general motor domain structure will be described based on the ΔMTBD-A monomer as it is the most comprehensive.
The motor domain is comprised of the oligomeric AAA+ ring, the linker, stalk and strut, and C sequence. Each AAA+ module has N-terminal ⍺/β-submodule and the carboxy-terminal ⍺-submodule - makes up the front and back face of the ring. AAA1-AAA4 have their own insertions in their ⍺/β-submodules, while AAA5 has an additional globular extension containing 8 ⍺-helices towards the back of the ring. A rod-like structural unit on the front face of the ring, the linker, has 19 ⍺-helices and 8 β-strands, which extends from the ⍺/β-submodule of AAA1 to the surface of the ring at AAA4. The Y-shaped part of the polypeptide between AAA4&5 of which one is shorter and the other longer, are the strut and stalk respectively. These findings were achieved through X-ray analysis.
The WT-A differ from the above description by having the MTBD present at the tip of stalk. Meanwhile, in WT-B, MTBD and the distal portion attached are absent from the stalk due to its flexibility. A C sequence is also present at the back face of the ring.
The WT-A differ from the above description by having the MTBD present at the tip of stalk. Meanwhile, in WT-B, MTBD and the distal portion attached are absent from the stalk due to its flexibility. A C sequence is also present at the back face of the ring.
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| Top view (left) and side view (right) of MTBD |
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