J. Biol. Chem., Vol. 265, Issue 31, 19362-19368, Nov, 1990
Lys-65 and Glu-168 are the residues for carbodiimide-catalyzed cross- linking between the two heads of rigor smooth muscle heavy meromyosin
H Onishi, T Maita, G Matsuda and K Fujiwara
Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka, Japan.
We have previously demonstrated that the two heads of chicken gizzard heavy
meromyosin (HMM) in a rigor complex with rabbit skeletal F-actin could be
cross-linked by the water-soluble carbodiimide 1-ethyl-3-[3-
(dimethylamino)propyl]carbodiimide. Here, we report the location of the
cross-linked sites in the amino acid sequence of the HMM heavy chain. One
of the cross-linked residues was identified as Glu-168 by sequencing the
CN1.CN6 cross-linked peptide containing residues 1-77 (CN1) and 164-203
(CN6). This site is located close to the ATP-binding site of HMM. Since the
other site was further into the amino acid sequence of CN1, another
cross-linked peptide corresponding to residues 53-66 and 145-182 was
isolated from the 1-ethyl-3-[3- (dimethylamino)propyl]carbodiimide-treated
acto-tryptic gizzard HMM digested further by other proteolytic enzymes. The
amino acid sequence of this peptide and its cyanogen bromide fragment
indicated that the cross-linking occurred between Glu-168 and Lys-65. Our
results suggests that these two amino acid side chains are in contact with
each other in the acto-gizzard HMM rigor complex and participate in the
electrostatic interaction between the two HMM heads bound to F-actin. Based
on the head-to-head contact, we propose a three-dimensional model for the
attachment of gizzard HMM heads to F-actin.