More myosin structure
More details of the myosin structure. When myosin is
exposed to the proteolytic
enzyme trypsin, fragmentation occurs in the middle of
the tail yielding heavy
meromyosin (HMM, molecular weight about 350,000) and
light meromyosin
(LMM, molecular weight about 150,000) HMM containing the
head and a short tail
can be further split by proteolytic enzymes, such as
papain, into subfragment 1 (S1,
molecular weight about 110,000) and subfragment 2 (S2).
The regions of proteolytic
fragmentation may serve as hinges. HMM and S1 bind
actin, hydrolyze ATP and are
water-soluble. LMM has no sites for actin or ATP
binding, but inherits the solubility
of myosin in 0.6 M KCl and the self-assembling property
of myosin in 0.03 M KCl.
S2 is water-soluble. Myosin and its proteolytic
fragments can be visualized by electron
microscopy