The effects of the interaction of myosin essential light chain isoforms with actin in skeletal muscles.

Abstract

In order to compare the ability of different isoforms of myosin essential light chain to interact with actin, the effect of the latter protein on the proteolytic susceptibility of myosin light chains (MLC-1S and MLC-1V - slow specific and same as ventricular isoform) from slow skeletal muscle was examined. Actin protects both slow muscle essential light chain isoforms from papain digestion, similarly as observed for fast skeletal muscle myosin (Nieznanska et al., 1998, Biochim. Biophys. Acta 1383: 71). The effect of actin decreases as ionic strength rises above physiological values for both fast and slow skeletal myosin, confirming the ionic character of the actin-essential light chain interaction. To better understand the role of this interaction, we examined the effect of synthetic peptides spanning the 10-amino-acid N-terminal sequences of myosin light chain 1 from fast skeletal muscle (MLC-1F) (MLCFpep: KKDVKKPAAA), MLC-1S (MLCSpep: KKDVPVKKPA) and MLC-1V (MLCVpep: KPEPKKDDAK) on the myofibrillar ATPase of fast and slow skeletal muscle. In the presence of MLCFpep, we observed an about 19% increase, and in the presence of MLCSpep about 36% increase, in the myofibrillar ATPase activity of fast muscle. On the other hand, in myofibrillar preparations from slow skeletal muscle, MLCSpep as well as MLCVpep caused a lowering of the ATPase activity by about 36%. The above results suggest that MLCSpep induces opposite effects on ATPase activity, depending on the type of myofibrils, but not through its specific N-terminal sequence - which differs from other MLC N-terminal peptides. Our observations lead to the conclusion that the action of different isoforms of long essential light chain is similar in slow and fast skeletal muscle. However the interaction of essential light chains with actin leads to different physiological effects probably depending on the isoforms of other myofibrillar proteins.

Myosin essential light chain 1sa decelerates actin and thin filament gliding on β-myosin molecules

“…S3). This N-terminal region of long ELC isoforms has been reported to interact transiently with actin filaments (Milligan et al .,1990), thus serving as a second actin binding site of myosin molecules (Miyanishi et al .,2002; Nieznańska et al ., 2002) and possibly modifying actomyosin interaction kinetics (Petzhold et al ., 2014; Sweeney, 1995; VanBuren et al ., 1994). Myosin preparations from soleus muscle tissue contained significant amounts of both ELC isoforms MLC1sa and MLC1sb with a higher relative content of MLC1sa (Fig.…”

The Structural Dynamics of Actin during Active Interaction with Myosin Depends on the Isoform of the Essential Light Chain

“…The physiological role of A1 in cardiac and skeletal muscle contractile activities was also studied using synthetic peptides corresponding to its 10–15 N-terminal amino acids. Addition of these peptides to muscle fibers or myofibrils increased their contractility and ATPase activity, − but the molecular target of these peptides has not been determined.…”

Myosin essential light chain 1sa decelerates actin and thin filament gliding on β-myosin molecules

“…S4 ). This N-terminal region of long ELC isoforms has been reported to interact transiently with actin filaments ( Milligan et al, 1990 ), thus serving as a second actin binding site of myosin molecules ( Miyanishi et al, 2002 ; Nieznańska et al, 2002 ) and possibly modifying actomyosin interaction kinetics ( Petzhold et al, 2014 ; Sweeney, 1995 ; VanBuren et al, 1994 ). Myosin preparations from M. soleus tissue contained significant amounts of both ELC isoforms MLC1sa and MLC1sb with a higher relative content of MLC1sa ( Fig.…”