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Myosin light chain phosphorylation and the cross-bridge cycle at low substrate concentration in chemically skinned guinea pig Taenia coli

Hellstrand, Per LU and Arner, Anders LU (1985) In Pflügers Archiv 405(4). p.323-328
Abstract
Force-velocity relations, rate of ATP turnover (JATP), and phosphorylation of the 20,000 D myosin light chains (LC20) were measured in chemically skinned guinea pig Taenia coli. Relative LC20 phosphorylation at 3.2 mM MgATP was 17% in relaxed tissues at pCa 9, and increased with force at increasing [Ca2+] to a maximum of 67% at pCa 4.5. Force at pCa 4.5 was dependent on the MgATP concentration with a half-maximal response at about 0.1 mM. At 0.1 mM MgATP LC20 phosphorylation at pCa 4.5 was 38%. Both JATP and the maximal shortening velocity (Vmax) were reduced in 0.1 mM MgATP, to 32% and 43%, respectively, of their values at 3.2 mM MgATP. Low-MgATP thus inhibits both LC20 phosphorylation and the extent and rate of cross-bridge interaction.... (More)
Force-velocity relations, rate of ATP turnover (JATP), and phosphorylation of the 20,000 D myosin light chains (LC20) were measured in chemically skinned guinea pig Taenia coli. Relative LC20 phosphorylation at 3.2 mM MgATP was 17% in relaxed tissues at pCa 9, and increased with force at increasing [Ca2+] to a maximum of 67% at pCa 4.5. Force at pCa 4.5 was dependent on the MgATP concentration with a half-maximal response at about 0.1 mM. At 0.1 mM MgATP LC20 phosphorylation at pCa 4.5 was 38%. Both JATP and the maximal shortening velocity (Vmax) were reduced in 0.1 mM MgATP, to 32% and 43%, respectively, of their values at 3.2 mM MgATP. Low-MgATP thus inhibits both LC20 phosphorylation and the extent and rate of cross-bridge interaction. High levels of LC20 phosphorylation, independent of Ca2+ and MgATP concentrations, were obtained by treatment with ATP-gamma-S. Maximal force at 3.2 mM MgATP after LC20 thiophosphorylation was unchanged, whereas halfmaximal force occurred at 0.065 mM MgATP after thiophosphorylation, compared to 0.13 mM after activation by Ca2+. The contraction in thiophosphorylated preparations at low-MgATP (0.1 mM) was associated with submaximal Vmax (60%) and JATP (27%). The results show that LC20 phosphorylation is correlated with the degree of force development in the Ca2+ activated contraction, both when Ca2+ and MgATP concentrations are varied. The reduced force and rate of crossbridge turnover in low MgATP are however primarily mediated by an influence of MgATP on the cross-bridge cycle, which is separate from the effect on LC20 phosphorylation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Smooth muscle, ATP, ATP-gamma-S, Ca2+, Force-velocity relation, Energetics
in
Pflügers Archiv
volume
405
issue
4
pages
323 - 328
publisher
Springer
external identifiers
  • pmid:3909097
  • scopus:0022382511
ISSN
0031-6768
DOI
10.1007/BF00595684
language
English
LU publication?
yes
id
a091d53f-8ed3-49ea-a865-b12c2062da66 (old id 1103430)
date added to LUP
2008-08-11 13:48:08
date last changed
2017-07-23 04:45:16
@article{a091d53f-8ed3-49ea-a865-b12c2062da66,
  abstract     = {Force-velocity relations, rate of ATP turnover (JATP), and phosphorylation of the 20,000 D myosin light chains (LC20) were measured in chemically skinned guinea pig Taenia coli. Relative LC20 phosphorylation at 3.2 mM MgATP was 17% in relaxed tissues at pCa 9, and increased with force at increasing [Ca2+] to a maximum of 67% at pCa 4.5. Force at pCa 4.5 was dependent on the MgATP concentration with a half-maximal response at about 0.1 mM. At 0.1 mM MgATP LC20 phosphorylation at pCa 4.5 was 38%. Both JATP and the maximal shortening velocity (Vmax) were reduced in 0.1 mM MgATP, to 32% and 43%, respectively, of their values at 3.2 mM MgATP. Low-MgATP thus inhibits both LC20 phosphorylation and the extent and rate of cross-bridge interaction. High levels of LC20 phosphorylation, independent of Ca2+ and MgATP concentrations, were obtained by treatment with ATP-gamma-S. Maximal force at 3.2 mM MgATP after LC20 thiophosphorylation was unchanged, whereas halfmaximal force occurred at 0.065 mM MgATP after thiophosphorylation, compared to 0.13 mM after activation by Ca2+. The contraction in thiophosphorylated preparations at low-MgATP (0.1 mM) was associated with submaximal Vmax (60%) and JATP (27%). The results show that LC20 phosphorylation is correlated with the degree of force development in the Ca2+ activated contraction, both when Ca2+ and MgATP concentrations are varied. The reduced force and rate of crossbridge turnover in low MgATP are however primarily mediated by an influence of MgATP on the cross-bridge cycle, which is separate from the effect on LC20 phosphorylation.},
  author       = {Hellstrand, Per and Arner, Anders},
  issn         = {0031-6768},
  keyword      = {Smooth muscle,ATP,ATP-gamma-S,Ca2+,Force-velocity relation,Energetics},
  language     = {eng},
  number       = {4},
  pages        = {323--328},
  publisher    = {Springer},
  series       = {Pflügers Archiv},
  title        = {Myosin light chain phosphorylation and the cross-bridge cycle at low substrate concentration in chemically skinned guinea pig Taenia coli},
  url          = {http://dx.doi.org/10.1007/BF00595684},
  volume       = {405},
  year         = {1985},
}