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Centrins are calmodulin-like proteins present in centrosomes and yeast spindle pole bodies (SPBs) and have essential functions in their duplication. The Saccharomyces cerevisiae centrin, Cdc31p, binds Sfi1p on multiple conserved repeats; both proteins localize to the SPB half-bridge, where the new SPB is assembled. The crystal structures of Sfi1p-centrin complexes containing several repeats show Sfi1p as an alpha helix with centrins wrapped around each repeat and similar centrin-centrin contacts between each repeat. Electron microscopy (EM) shadowing of an Sfi1p-centrin complex with 15 Sfi1 repeats and 15 centrins bound showed filaments 60 nm long, compatible with all the Sfi1 repeats as a continuous alpha helix. Immuno-EM localization of the Sfi1p N and C termini showed Sfi1p-centrin filaments spanning the length of the half-bridge with the Sfi1p N terminus at the SPB. This suggests a model for SPB duplication where the half-bridge doubles in length by association of the Sfi1p C termini, thereby providing a new Sfi1p N terminus to initiate SPB assembly.

Original publication




Journal article


J Cell Biol

Publication Date





867 - 877


Binding Sites, Calcium-Binding Proteins, Cell Cycle Proteins, Crystallography, X-Ray, Mass Spectrometry, Microtubule Proteins, Models, Molecular, Protein Binding, Protein Structure, Tertiary, Repetitive Sequences, Amino Acid, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Analysis, Protein, Spindle Apparatus