M. Watanabe et al., MAPPING PHOSPHORYLATION SITE OF THE REGULATORY LIGHT-CHAIN IN SMOOTH-MUSCLE MYOSIN BY IMMUNOELECTRON MICROSCOPY, Proceedings of the Japan Academy. Series B Physical and biological sciences, 74(2), 1998, pp. 31-34
Phosphorylation site responsible Ibr the regulation of smooth muscle m
yosin was mapped using a polyclonal antibody against a phosphorylated
hendecapeptide corresponding to the amino acid sequence around Ser-19
in the regulatory light chain. Phosphorylated myosin mixed with the an
tibody was rotary-shadowed and was examined by electron microscopy. Th
e antibody binding site was located in the head portion of myosin and
the average distance from the head-rod junction was about 3 nm toward
the tip of myosin head. The results indicate that the phosphorylated S
er-19 in regulatory light chain is a little more extended toward the a
djacent essential light chain in reference to the resolved N-terminal
residues of the regulatory light chain in the three dimensional struct
ure of myosin :leads from other sources, in which the structure of the
N-terminal portions homologous to the phosphorylated Ser-19 was not r
esolved (Rayment, I. et al. (1993) Science 261, 50-58; Xie, X. et al.
(1994) Nature 368, 306-312). Intramolecular interaction through the in
troduced phosphoryl group may be the primary results in the regulatory
light chain which releases the motor domain from its suppressed state
.