7ung
48-nm repeat of the human respiratory doublet microtubule
Structural highlights
FunctionCP141_HUMAN Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating.[1] Publication Abstract from PubMedThe cilium-centrosome complex contains triplet, doublet, and singlet microtubules. The lumenal surfaces of each microtubule within this diverse array are decorated by microtubule inner proteins (MIPs). Here, we used single-particle cryo-electron microscopy methods to build atomic models of two types of human ciliary microtubule: the doublet microtubules of multiciliated respiratory cells and the distal singlet microtubules of monoflagellated human spermatozoa. We discover that SPACA9 is a polyspecific MIP capable of binding both microtubule types. SPACA9 forms intralumenal striations in the B tubule of respiratory doublet microtubules and noncontinuous spirals in sperm singlet microtubules. By acquiring new and reanalyzing previous cryo-electron tomography data, we show that SPACA9-like intralumenal striations are common features of different microtubule types in animal cilia. Our structures provide detailed references to help rationalize ciliopathy-causing mutations and position cryo-EM as a tool for the analysis of samples obtained directly from ciliopathy patients. SPACA9 is a lumenal protein of human ciliary singlet and doublet microtubules.,Gui M, Croft JT, Zabeo D, Acharya V, Kollman JM, Burgoyne T, Hoog JL, Brown A Proc Natl Acad Sci U S A. 2022 Oct 11;119(41):e2207605119. doi: , 10.1073/pnas.2207605119. Epub 2022 Oct 3. PMID:36191189[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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