2024年12月24日 (二) 07:26 长河

2024-12-24T07:26:46Z

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Cohesin. Cohesin is a
protein complex with four subunits.
(A) Two subunits of cohesin are members
of a large family of proteins called SMC
proteins (for structural maintenance of
chromosomes). These subunits, Smc1
and Smc3, are coiled-coil proteins whose
N- and C-terminal regions fold together
to form a globular ATPase domain.
(B) The Scc1 subunit contains two globular
domains separated by a long disordered
region that binds an additional subunit
called Scc3. Binding of the globular
domains of Scc1 to the Smc1 and Smc3
subunits results in a ring structure that
encircles the sister chromatids as shown in
(C). ATP binding promotes the interaction
of the ATPase domains as shown here,
while ATP hydrolysis dissociates the
ATPase domains. Loading and unloading
of cohesin on DNA requires ATP hydrolysis
and is expected to involve the opening of
one of the three intersubunit gates, but
this process remains poorly understood.
During S phase, acetylation of the ATPase
domain of Smc3 (not shown) prevents
the opening of the ring, thereby locking the
cohesin ring around the sister chromatids.
In metaphase, proteolytic cleavage of
sites in the disordered region of Scc1
triggers sister-chromatid separation, as
discussed later.

文件:细胞17-23.png - 版本历史

2024年12月24日 (二) 07:26 长河