The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes.

Royle’s Pika Ochotona roylei is high altitude animal belonging to the family Ochotonidae in order Lagomorpha. Royle’s Pika was reported in different locations between an elevation of 2180 to 5950 meters above sea level (m asl). This study carried in February and October 2017 recorded a small population of Royle’s Pika in the Parvati Kunda Groundwater Complex of Gatlang village in Rasuwa District, Nepal. A total of 12 Royle’s pika individuals were head counted from three sites while Pika foraged plants were observed in other sites. Pika was observed in talus groove amidst Rhododendron-fir forest, Fir-hemlock forest, and Rhododendron shrub close to the alpine meadow. Pika in the study was distributed from the Parvati Kunda wetland proximity at an elevation of 2605 m with a direct count of 2 individuals to an elevation of 3000 m asl beneath Tshumer hill with a headcount of 7 individuals. However, the population of Royle’s Pika in the area was estimated more. The population density of 6 individuals/hectare was calculated in the area, which is relatively lower than the population density accounted for in other areas.

molecules per filament to determine the relationship between the number of heads and velocity. 25:75, and 15:25 ratios) were approximately the same length as normal SMM filaments (~0.6 mm), and the number of molecules incorporated was directly related to the ratio of SMM to rods. As the number of heads decreased, the maximal velocity at saturating ATP also decreased, and the K ATP was lower for all of the cofilaments compared to the normal filaments. These findings provide evidence that the velocity of SMM filaments is influenced by attachment limited kinetics. The longer SMM filaments (average length of 2.3 5 0.81 mm) will allow us to visualize the geometry of acto-myosin interactions during motion. Also, the relationship between velocity and filament length will be determined at various [ATP]. The long filaments also better demonstrate our previously described ''parking'' behavior where filaments move to the end of actin filaments but remain attached for long periods even at saturating [ATP] (Haldeman et al, JBC, 2014). Interestingly, most of the SMM filament hangs off the end of the actin suggesting the parking is mediated by a small fraction of the heads.