Maintenance of caspase-3 proenzyme dormancy by an intrinsic “safety catch” regulatory tripeptide

Caspase-3 is synthesized as a dormant proenzyme and is maintained in an inactive conformation by an Asp-Asp-Asp “safety-catch” regulatory tripeptide contained within a flexible loop near the large-subunit/small-subunit junction. Removal of this “safety catch” results in substantially enhanced autocatalytic maturation as well as increased vulnerability to proteolytic activation by upstream proteases in the apoptotic pathway such as caspase-9 and granzyme B. The safety catch functions through multiple ionic interactions that are disrupted by acidification, which occurs in the cytosol of cells during the early stages of apoptosis. We propose that the caspase-3 safety catch is a key regulatory checkpoint in the apoptotic cascade that regulates terminal events in the caspase cascade by modulating the triggering of caspase-3 activation.

An in vitro assay reveals essential protein components for the “catch” state of invertebrate smooth muscle

“Catch,” a state where some invertebrate muscles sustain high tension over long periods of time with little energy expenditure (low ATP hydrolysis rate) is similar to the “latch” state of vertebrate smooth muscles. Its induction and release involve Ca2+-dependent phosphatase and cAMP-dependent protein kinase, respectively. Molecular mechanisms for catch remain obscure. Here, we describe a quantitative microscopic in vitro assay reconstituting the catch state with proteins isolated from catch muscles. Thick filaments attached to glass coverslips and pretreated with ≈10−4 M free Ca2+ and soluble muscle proteins bound fluorescently labeled native thin filaments tightly in catch at ≈10−8 M free Ca2+ in the presence of MgATP. At ≈10−4 M free Ca2+, the thin filaments moved at ≈4 μm/s. Addition of cAMP and cAMP-dependent protein kinase at ≈10−8 M free Ca2+ caused their release. Rabbit skeletal muscle F-actin filaments completely reproduced the results obtained with native thin filaments. Binding forces >500 pN/μm between thick and F-actin filaments were measured by glass microneedles, and were sufficient to explain catch tension in vivo. Synthetic filaments of purified myosin and twitchin bound F-actin in catch, showing that other components of native thick filaments such as paramyosin and catchin are not essential. The binding between synthetic thick filaments and F-actin filaments depended on phosphorylation of twitchin but not of myosin. Cosedimentation experiments showed that twitchin did not bind directly to F-actin in catch. These results show that catch is a direct actomyosin interaction regulated by twitchin phosphorylation.

Response of Catch-Per-Unit-Effort to Spatial and Environmental Factors: an Exploratory Data Analysis Using Generalized Additive Models

Understanding spatial distributions and how environmental conditions influence catch-per-unit-effort (CPUE) is important for increased fishing efficiency and sustainable fisheries management. This study investigated the relationship between CPUE, spatial factors, temperature, and depth using generalized additive models. Combinations of factors, and not one single factor, were frequently included in the best model. Parameters which best described CPUE varied by geographic region. The amount of variance, or deviance, explained by the best models ranged from a low of 29% (halibut, Charlotte region) to a high of 94% (sablefish, Charlotte region). Depth, latitude, and longitude influenced most species in several regions. On the broad geographic scale, depth was associated with CPUE for every species, except dogfish. Latitude and longitude influenced most species, except halibut (Areas 4 A/D), sablefish, and cod. Temperature was important for describing distributions of halibut in Alaska, arrowtooth flounder in British Columbia, dogfish, Alaska skate, and Aleutian skate. The species-habitat relationships revealed in this study can be used to create improved fishing and management strategies.

Croatia and the EU: the catch-up issue. CEPS Commentary, 28 June 2013

To become a prosperous country devoid of institutional preconditions for corruption, Croatia will have to define its own goals, persevere in reaching them and introduce some sort of internal monitoring. True political will, democratisation, government accountability and appropriate policies are crucial, particularly for the institutions and mechanisms that monitor government accountability and citizen participation. One can only reiterate the European Commission’s hope that membership will prove to be an additional incentive to Croatia’s politicians to change their behaviour and start addressing state capture in the country.