Effect of myosin cross-bridge interaction with actin on the Ca2+-binding properties of troponin C in fast skeletal myofibrils

Sachio Morimoto

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Ca2+ binding to fast skeletal muscle troponin C reincorporated into troponin C-depleted (CDTA-treated) myofibrils has been measured directly by using 45Ca and indirectly by using a fluorescent probe. Direct Ca2+-binding measurements have shown that the Ca2+ affinity of the low-affinity sites is enhanced in the absence of ATP and conversely reduced when myosin is selectively extracted from myofibrils, compared to the Ca2+ affinity in the presence of ATP. Fluorescence intensity changes of a dansylaziridine label at the Met-25 residue of troponin C have shown the same Ca2+-sensitivity whether or not ATP is present, while much lower Ca2+-sensitivity is seen in the myosin-extracted myofibrils. Since the Met-25 residue is in the amino terminal side α-helix of Ca2+-binding site I and far from Ca2+-binding site II in the primary structure, Ca2+ binding to site II has been evaluated by assuming that the fluorescence change monitors Ca2+ binding to site I alone. Ca2+ binding to site II thus estimated has shown high positive cooperativity only in the presence of ATP and has been found to be nearly proportional to the activation of myofibrillar ATPase, suggesting that Ca2+-binding site II is directly involved in the activation of myofibrillar ATPase activity. On the other hand, Ga2+-binding site I has been suggested to regulate the interaction of weakly binding cross-bridges with the thin filament, since the fluorescence change in the presence of ATP is saturated at the free Ca2+ concentration required for the activation of myofibrillar ATPase.

Original languageEnglish
Pages (from-to)120-126
Number of pages7
JournalJournal of Biochemistry
Volume109
Issue number1
DOIs
Publication statusPublished - Jan 1 1991

Fingerprint

Troponin C
Myofibrils
Myosins
Actins
Adenosine Triphosphate
Binding Sites
Fluorescence
Chemical activation
Adenosine Triphosphatases
Calcium-Transporting ATPases
Fluorescent Dyes
Muscle
Labels
Skeletal Muscle

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

Cite this

Effect of myosin cross-bridge interaction with actin on the Ca2+-binding properties of troponin C in fast skeletal myofibrils. / Morimoto, Sachio.

In: Journal of Biochemistry, Vol. 109, No. 1, 01.01.1991, p. 120-126.

Research output: Contribution to journalArticle

@article{b7e5056d764044a38355ebb56dbe749f,
title = "Effect of myosin cross-bridge interaction with actin on the Ca2+-binding properties of troponin C in fast skeletal myofibrils",
abstract = "Ca2+ binding to fast skeletal muscle troponin C reincorporated into troponin C-depleted (CDTA-treated) myofibrils has been measured directly by using 45Ca and indirectly by using a fluorescent probe. Direct Ca2+-binding measurements have shown that the Ca2+ affinity of the low-affinity sites is enhanced in the absence of ATP and conversely reduced when myosin is selectively extracted from myofibrils, compared to the Ca2+ affinity in the presence of ATP. Fluorescence intensity changes of a dansylaziridine label at the Met-25 residue of troponin C have shown the same Ca2+-sensitivity whether or not ATP is present, while much lower Ca2+-sensitivity is seen in the myosin-extracted myofibrils. Since the Met-25 residue is in the amino terminal side α-helix of Ca2+-binding site I and far from Ca2+-binding site II in the primary structure, Ca2+ binding to site II has been evaluated by assuming that the fluorescence change monitors Ca2+ binding to site I alone. Ca2+ binding to site II thus estimated has shown high positive cooperativity only in the presence of ATP and has been found to be nearly proportional to the activation of myofibrillar ATPase, suggesting that Ca2+-binding site II is directly involved in the activation of myofibrillar ATPase activity. On the other hand, Ga2+-binding site I has been suggested to regulate the interaction of weakly binding cross-bridges with the thin filament, since the fluorescence change in the presence of ATP is saturated at the free Ca2+ concentration required for the activation of myofibrillar ATPase.",
author = "Sachio Morimoto",
year = "1991",
month = "1",
day = "1",
doi = "10.1093/oxfordjournals.jbchem.a123331",
language = "English",
volume = "109",
pages = "120--126",
journal = "Journal of Biochemistry",
issn = "0021-924X",
publisher = "Oxford University Press",
number = "1",

}

TY - JOUR

T1 - Effect of myosin cross-bridge interaction with actin on the Ca2+-binding properties of troponin C in fast skeletal myofibrils

AU - Morimoto, Sachio

PY - 1991/1/1

Y1 - 1991/1/1

N2 - Ca2+ binding to fast skeletal muscle troponin C reincorporated into troponin C-depleted (CDTA-treated) myofibrils has been measured directly by using 45Ca and indirectly by using a fluorescent probe. Direct Ca2+-binding measurements have shown that the Ca2+ affinity of the low-affinity sites is enhanced in the absence of ATP and conversely reduced when myosin is selectively extracted from myofibrils, compared to the Ca2+ affinity in the presence of ATP. Fluorescence intensity changes of a dansylaziridine label at the Met-25 residue of troponin C have shown the same Ca2+-sensitivity whether or not ATP is present, while much lower Ca2+-sensitivity is seen in the myosin-extracted myofibrils. Since the Met-25 residue is in the amino terminal side α-helix of Ca2+-binding site I and far from Ca2+-binding site II in the primary structure, Ca2+ binding to site II has been evaluated by assuming that the fluorescence change monitors Ca2+ binding to site I alone. Ca2+ binding to site II thus estimated has shown high positive cooperativity only in the presence of ATP and has been found to be nearly proportional to the activation of myofibrillar ATPase, suggesting that Ca2+-binding site II is directly involved in the activation of myofibrillar ATPase activity. On the other hand, Ga2+-binding site I has been suggested to regulate the interaction of weakly binding cross-bridges with the thin filament, since the fluorescence change in the presence of ATP is saturated at the free Ca2+ concentration required for the activation of myofibrillar ATPase.

AB - Ca2+ binding to fast skeletal muscle troponin C reincorporated into troponin C-depleted (CDTA-treated) myofibrils has been measured directly by using 45Ca and indirectly by using a fluorescent probe. Direct Ca2+-binding measurements have shown that the Ca2+ affinity of the low-affinity sites is enhanced in the absence of ATP and conversely reduced when myosin is selectively extracted from myofibrils, compared to the Ca2+ affinity in the presence of ATP. Fluorescence intensity changes of a dansylaziridine label at the Met-25 residue of troponin C have shown the same Ca2+-sensitivity whether or not ATP is present, while much lower Ca2+-sensitivity is seen in the myosin-extracted myofibrils. Since the Met-25 residue is in the amino terminal side α-helix of Ca2+-binding site I and far from Ca2+-binding site II in the primary structure, Ca2+ binding to site II has been evaluated by assuming that the fluorescence change monitors Ca2+ binding to site I alone. Ca2+ binding to site II thus estimated has shown high positive cooperativity only in the presence of ATP and has been found to be nearly proportional to the activation of myofibrillar ATPase, suggesting that Ca2+-binding site II is directly involved in the activation of myofibrillar ATPase activity. On the other hand, Ga2+-binding site I has been suggested to regulate the interaction of weakly binding cross-bridges with the thin filament, since the fluorescence change in the presence of ATP is saturated at the free Ca2+ concentration required for the activation of myofibrillar ATPase.

UR - http://www.scopus.com/inward/record.url?scp=0025959189&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0025959189&partnerID=8YFLogxK

U2 - 10.1093/oxfordjournals.jbchem.a123331

DO - 10.1093/oxfordjournals.jbchem.a123331

M3 - Article

C2 - 1826677

AN - SCOPUS:0025959189

VL - 109

SP - 120

EP - 126

JO - Journal of Biochemistry

JF - Journal of Biochemistry

SN - 0021-924X

IS - 1

ER -