Regulation of the actin-myosin interaction by titin.
Titin is known to interact with actin thin filaments within the I-band region of striated muscle sarcomeres. In this study, we have used a titin fragment of 800 kDa (T800) purified from striated skeletal muscle to measure the effect of this interaction on the functional properties of the actin-myosin complex. MALDI-TOF MS revealed that T800 contains the entire titin PEVK (Pro, Glu, Val, Lys-rich) domain. In the presence of tropomyosin-troponin, T800 increased the sliding velocity (both average and maximum values) of actin filaments on heavy-meromyosin (HMM)-coated surfaces and dramatically decreased the number of stationary filaments. These results were correlated with a 30% reduction in actin-activated HMM ATPase activity and with an inhibition of HMM binding to actin N-terminal residues as shown by chemical cross-linking. At the same time, T800 did not affect the efficiency of the Ca(2+)-controlled on/off switch, nor did it alter the overall binding energetics of HMM to actin, as revealed by cosedimentation experiments. These data are consistent with a competitive effect of PEVK domain-containing T800 on the electrostatic contacts at the actin-HMM interface. They also suggest that titin may participate in the regulation of the active tension generated by the actin-myosin complex.
Niederländer
Nicolas
N
CRBM-CNRS, Montpellier, France.
Raynaud
Fabrice
F
Astier
Catherine
C
Chaussepied
Patrick
P
D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D064211:Connectin; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology; D006801:Humans; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011817:Rabbits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014335:Tropomyosin / Q000737:chemistry / Q000378:metabolism; D014336:Troponin / Q000737:chemistry / Q000378:metabolism
D000199:Actins; D064211:Connectin; D003432:Cross-Linking Reagents; D009124:Muscle Proteins; D015879:Myosin Subfragments; D010446:Peptide Fragments; C577285:TTN protein, human; D014335:Tropomyosin; D014336:Troponin; D011494:Protein Kinases; D000251:Adenosine Triphosphatases; D005022:Ethyldimethylaminopropyl Carbodiimide