Purification and characterization of the mammalian myosin light chain phosphatase holoenzyme. The differential effects of the holoenzyme and its subunits on smooth muscle.

Journal Article (Journal Article)

We have purified to homogeneity from the myofibrillar fraction of pig bladder a mammalian heterotrimeric form of PP-1, SMPP-1M. Purified pig bladder SMPP-1M is similar in composition and substrate specificity to avian gizzard PP-1M reported by Alessi et al. (Alessi, D., Macdougall, L. K., Sola, M. M., Ikebe, M., and Cohen, P. (1992) Eur. J. Biochem. 210, 1023-1035) and consists of the catalytic subunit of PP-1 (37 kDa) and two other equimolar subunits of 130 and 20 kDa. The properties of SMPP-1M and the role of its regulatory subunits in the dephosphorylation of myosin and in the initiation of relaxation were characterized both in vitro and in smooth muscle. We show that the relaxant effect of the catalytic subunit in smooth muscle is markedly potentiated by the addition of the regulatory subunits of SMPP-1M. Our findings demonstrate that SMPP-1M is the major phosphatase dephosphorylating myosin in mammalian smooth muscle and that myosin dephosphorylation is regulated in vivo via targeting subunits that specifically alter the substrate specificity of PP-1C toward myosin.

Full Text

Duke Authors

Cited Authors

  • Shirazi, A; Iizuka, K; Fadden, P; Mosse, C; Somlyo, AP; Somlyo, AV; Haystead, TA

Published Date

  • December 16, 1994

Published In

Volume / Issue

  • 269 / 50

Start / End Page

  • 31598 - 31606

PubMed ID

  • 7989330

International Standard Serial Number (ISSN)

  • 0021-9258


  • eng

Conference Location

  • United States