Figure 2. 16 nm structure of Chlamydomonas doublet.
(A, B) 16 nm repeat structure of Chlamydomonas doublet and model at the IJ region. Tubulin densities are depicted as transparent gray, except in A in which tubulins are shown in dark blue. (C) Atomic model of the IJ complex, consisting of PACRG, FAP20, FAP52 and FAP276. Color scheme: FAP20: dark green; PACRG: gray; FAP52: light green, FAP276: purple; tubulin: transparent gray density. (D, E) Maps and models of PF A1 and B10, and IJ PF illustrating how the IJ PF interacts with tubulins. The views are indicated in the schematics. Dashed boxes indicate the views in (F), (G) and (H). Color scheme: α-tubulin: green; β-tubulin: blue; PACRG: gray; FAP20: dark green; FAP276: purple. (F) Electrostatic surface charge of PACRG, FAP20 and α- and β-tubulins of PF A1. Tubulin surface is negatively charged while the interacting interface of PACRG and FAP20 are positively charged. (G) The interaction of the PACRG with the inter-dimer interface of tubulins from PF B10 is shown. H136 from PACRG is conserved and is likely to take part in the interaction with D127 and C129 from α-tubulin of PF B10. (H) The C-terminus of β-tubulin of PF A1 interacts with PACRG and FAP20. Potential residues involved in the interaction of C-tail of β-tubulin and PACRG and FAP20 are shown. (I) Chlamydomonas PACRG has a long N-terminus 1–117. The N-terminus of Chlamydomonas PACRG (red) forms a stable triple helix arrangement with the core of the protein. This is not observed in the human PACRG (PDB: 6NDU) shown in yellow. In addition, the N-terminus of PACRG going into the wedge between PF A13 and A1.
Figure 2—figure supplement 1. Atomic models of PACRG, FAP20, FAP52 and FAP276.
