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Fig. 1.13 Sas-6 homomers as the building block of centriole central tubule. Sas-6 forms
homomers in the cytosol. These tetramers are hypothesized to polymerize and form the central
tubule of the centriole (Gopalakrishnan et al.
2010
). (Illustrated by Iwasa, Janet Haru)
Fig. 1.14 S-CAP complex. a Sas-4 forms a complex known as S-CAP together with Cnn, Asl,
and D-PLP. This complex also contains CP190 and Tubulin. b S-CAP complexes are tethered to
the centrosome via Sas-4 and contribute to the formation of the PCM (Gopalakrishnan et al. in
press) (The fig is modified from Fig.
1.7
(Gopalakrishnan et al.
2011
)
1.7 Identification of Centrosomal Complexes
Drosophila embryos are a rich source for centrosomal protein complexes (Go-
palakrishnan et al. in press; Kellogg and Alberts
1992
; Moritz et al.
1995
).
Originally, this system was used to isolate CP190 and CP60 complexes, which are
nuclear and centrosomal proteins (Kellogg and Alberts
1992
; Kellogg et al.
1995
).
Later, this system was used to purify c-TuRC and c-TuSC complexes, which are
found in the cytosol and reside in the PCM (Moritz et al.
1998
; Oegema et al.
1999
). More recently, drosophila embryos were used to isolate complexes of
specific centrosomal proteins such Sas-6 (Gopalakrishnan et al.
2010
) and Sas-4
(Gopalakrishnan et al. in press). Sas-6 forms homomers that are hypothesized to be
the building block of the centriole central tubule (Gopalakrishnan et al.
2010
;
Kitagawa et al.
2011
; van Breugel et al.
2011
) (Fig.
1.13
).
Sas-4 forms a complex (named S-CAP) with the centrosomal proteins CNN,
Asl, and D-PLP (Gopalakrishnan et al.
2011
) (Fig.
1.14
). Interestingly, mutations
in the orthologs of these proteins results in microcephaly, a developmental dis-
order where brain size is severely reduced (Al-Dosari et al.
2010
; Bond et al.
2005
;
