Fractionation and isolation of heparan sulfates using poly-L-lysine-Sepharose

Polylysine binding to unphosphorylated smooth muscle myosin enhances formation and stabilizes myosin filaments in vitro

Previously, we demonstrated that positively charged polylysine, our model for biological polyamines, activates the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin and shifts the myosin conformation from the folded 10S to linear 6S form. These effects of polylysine were reversed by the oppositely charged heparin (Szymanski et al. (1993) Am J Physiol 265, C379). In the present report, we provide further information on polylysine binding to smooth muscle myosin, and test the hypothesis that polylysine binding to unphosphorylated myosin involves filament formation. To relate the effects of polylysine on contractility in smooth muscle to physiologically relevant material, we investigated the ability of naturally occurring positively charged polyamines, histones, cadaverine, putrescine and spermidine to activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. Our data show that polylysine binding to individual unphosphorylated myosin molecules stimulates formation of myosin filaments. Polylysine also interacts with myosin filaments, causing enhancement of their size and the numbers, and this could be reversed by heparin. Polylysine binding to myosin filaments made them more resistant to disassembly by high salt concentrations (KCl) or ATP. Naturally occurring polyamines in millimolar concentrations activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. We suggest that the electrostatic interactions between naturally occurring positively charged polyamines and unphosphorylated smooth muscle myosin may play a role in stabilization of thick filament structurein situ.

Polylysine activates smooth muscle myosin ATPase activity via induction of a 10S to 6S transition

Polylysine (10-13 kDa) stimulates contraction in smooth muscle skinned fibers and activates actomyosin adenosinetriphosphatase (ATPase) activity in the absence of myosin light chain phosphorylation [P. T. Szymanski and R. J. Paul. Adv. Exp. Med. 304: 363-368, 1991; P. T. Szymanski, J. D. Strauss, G. Doerman, J. DiSalvo, and R. J. Paul. Am J. Physiol. 262 (Cell Physiol. 31): C1445-C1455, 1992]. To provide further information on the mechanism of polylysine action on contractility in smooth muscle, we investigated its effect on ATPase activity and conformation of purified gizzard myosin. We report here that polylysine directly stimulates myosin ATPase activity in a concentration-dependent manner. This stimulation could be completely abolished with the addition of heparin, a negatively charged heteropolysaccharide. Polylysine (10 microM) increases myosin ATPase activity to a level similar to that of myosin phosphorylation. Addition of 10 microM polylysine to phosphorylated myosin [with myosin light chain kinase and adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), to approximately 1.9 mol P/mol myosin], however, did not further stimulate ATPase activity. At 0.2 M KCl (the salt concentration at which myosin exists primary in the 10S form), the addition of polylysine increases myosin ATPase activity to a level comparable to that of untreated myosin in 0.3 M KCl. These changes parallel the increase in solution viscosity elicited by polylysine. These results suggest that polylysine induces a transition in myosin conformation from the 10S to the 6S form, and this was confirmed by electron microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Polylysine activates smooth muscle actin-myosin interaction without LC20 phosphorylation

Phosphorylation/dephosphorylation of the 20-kDa light chain of smooth muscle myosin is a major regulator of actin-myosin interaction. Phosphatase inhibitors have thus been shown to enhance contraction in smooth muscle. The activity of type II phosphatase against phosphorylated myosin light chains is inhibited by polylysine. Thus we studied the effects of polylysine (10-13 kDa) on actin-myosin interaction in permeabilized guinea pig taenia coli fibers and in bovine aortic actomyosin. Addition of polylysine (10-20 microM) to Ca-ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid buffered solution ([Ca2+] less than 0.01 microM) elicited a contraction in fibers of 40 +/- 8% (n = 6) of maximally stimulated contractions ([Ca2+] congruent to 1.5 microM). Untreated fibers did not generate any significant force in parallel control experiments. Similarly, polylysine stimulated the ATPase activity both in fibers and actomyosin in a dose-dependent manner. This stimulation could be completely inhibited and abolished upon addition of heparin, a negatively charged heteropolysaccharide. In actomyosin previously phosphorylated with ATP gamma S, polylysine in a concentration range of 2-13 microM did not further stimulate enzyme activity. These increases in activity were not connected with significant changes in the phosphorylation of 20-kDa myosin light chain nor could any incorporation of 32P associated with polylysine stimulation be detected in both skinned fibers and actomyosin by autoradiography of SDS gels. Our data indicate that polylysine increases actin-myosin interaction in both smooth muscle model systems by directly influencing contractile proteins. As such, polylysine may be a useful probe for the mechanism of activation of smooth muscle.

The basis and applicability of the dimethylmethylene blue binding assay for sulfated glycosaminoglycans

A rapid spectrophotometric assay for sulfated glycosaminoglycans, based on reaction of these compounds with the dye 1,9-dimethylmethylene blue (DMMB), is gaining widespread acceptance. The limitations of the assay have not been explored, and we have investigated the absorption spectra of the dye in the presence of a variety of compounds in order to understand the mechanism of colour formation. The dye exhibits classical metachromasia in the presence of sulfated glycosaminoglycans, but appears to do so by a much simpler mechanism than other thiazine dyes such as Azure A. Evidence is offered to support the conclusion that dye dimer reacts with the polyanion to produce a single metachromatic species by ionic perturbation of the chromophore. As predicted, factors which disrupt dimerization, such as pyridine and pyridine nucleotides, preclude use of the assay in their presence, and high salt concentrations can give false positive readings by inducing metachromasia in the absence of polyanion. When these factors are understood, the assay can be used with convenience. In particular, it allows direct measurement of the glycosaminoglycan content of a few mg of alkaline-solubilized basement membrane.

Distribution of mucus glycoprotein in four compartments of lamb and sheep stomach

The regional distribution of mucus glycoprotein in lamb before weaning and sheep was studied. Mucus glycoprotein was present in the forestomach region of lamb and glandular stomach (abomasum) of lamb and sheep. Ester sulfates were found in all mucus glycoproteins obtained.