title: Maximum limit to the number of myosin II motors participating in processive sliding of actin.
abstract: In this work, we analysed processive sliding and breakage of actin filaments at various heavy meromyosin (HMM) densities and ATP concentrations in IVMA. We observed that with addition of ATP solution, the actin filaments fragmented stochastically; we then determined mean length and velocity of surviving actin filaments post breakage. Average filament length decreased with increase in HMM density at constant ATP, and increased with increase in ATP concentration at constant HMM density. Using density of HMM molecules and length of actin, we estimated the number of HMM molecules per actin filament (N) that participate in processive sliding of actin. N is solely a function of ATP concentration: 88 ± 24 and 54 ± 22 HMM molecules (mean ± S.D.) at 2 mM and 0.1 mM ATP respectively. Processive sliding of actin filament was observed only when N lay within a minimum lower limit (Nmin) and a maximum upper limit (Nmax) to the number of HMM molecules. When N < Nmin the actin filament diffused away from the surface and processivity was lost and when N > Nmax the filament underwent breakage eventually and could not sustain processive sliding. We postulate this maximum upper limit arises due to increased number of strongly bound myosin heads.
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
authors.forename: Khushboo
authors.initials: K
authors.lastname: Rastogi
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
authors.forename: Mohammed Shabeel
authors.initials: MS
authors.lastname: Puliyakodan
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology, New Delhi 110016, India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Pandey
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Nath
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
authors.forename: Ravikrishnan
authors.initials: R
authors.lastname: Elangovan
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002645:Chickens; D018482:Muscle, Skeletal / Q000166:cytology; D015879:Myosin Subfragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism*
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D000255:Adenosine Triphosphate; D024462:Myosin Type II