Differential actin binding along the PEVK domain of skeletal muscle titin.
Parts of the PEVK (Pro-Glu-Val-Lys) domain of the skeletal muscle isoform of the giant intrasarcomeric protein titin have been shown to bind F-actin. However, the mechanisms and physiological function of this are poorly understood. To test for actin binding along PEVK, we expressed contiguous N-terminal (PEVKI), middle (PEVKII), and C-terminal (PEVKIII) PEVK segments of the human soleus muscle isoform. We found a differential actin binding along PEVK in solid-state binding, cross-linking and in vitro motility assays. The order of apparent affinity is PEVKII>PEVKI>PEVKIII. To explore which sequence motifs convey the actin-binding property, we cloned and expressed PEVK fragments with different motif structure: PPAK, polyE-rich and pure polyE fragments. The polyE-containing fragments had a stronger apparent actin binding, suggesting that a local preponderance of polyE motifs conveys an enhanced local actin-binding property to PEVK. The actin binding of PEVK may serve as a viscous bumper mechanism that limits the velocity of unloaded muscle shortening towards short sarcomere lengths. Variations in the motif structure of PEVK might be a method of regulating the magnitude of the viscous drag.
Nagy
Attila
A
Department of Biophysics, University of Pécs, Faculty of Medicine, Szigeti út 12. Pécs 7624, Hungary.
Cacciafesta
Paola
P
Grama
László
L
Kengyel
András
A
Málnási-Csizmadia
András
A
Kellermayer
Miklós S Z
MS
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry; D020816:Amino Acid Motifs; D000818:Animals; D002118:Calcium / Q000737:chemistry; D002465:Cell Movement; D064211:Connectin; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015723:Gene Library; D006801:Humans; D009124:Muscle Proteins / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D011189:Potassium Chloride / Q000737:chemistry; D011485:Protein Binding; D020033:Protein Isoforms; D011494:Protein Kinases / Q000502:physiology*; D017434:Protein Structure, Tertiary; D013997:Time Factors
D000199:Actins; D064211:Connectin; D018076:DNA, Complementary; D009124:Muscle Proteins; D020033:Protein Isoforms; C577285:TTN protein, human; D011189:Potassium Chloride; D011494:Protein Kinases; D000251:Adenosine Triphosphatases; D002118:Calcium