Mechanism of autocatalytic activation during proteasome assembly.

Many large molecular machines are too elaborate to assemble spontaneously and are built through ordered pathways orchestrated by dedicated chaperones. During assembly of the core particle (CP) of the proteasome, where protein degradation occurs, its six active sites are simultaneously activated via cleavage of N-terminal propeptides. Such activation is autocatalytic and coupled to fusion of two half-CP intermediates, which protects cells by preventing activation until enclosure of the active sites within the CP interior. Here we uncover key mechanistic aspects of autocatalytic activation, which proceeds through alignment of the ß5 and ß2 catalytic triad residues, respectively, with these triads being misaligned before fusion. This mechanism contrasts with most other zymogens, in which catalytic centers are preformed. Our data also clarify the mechanism by which individual subunits can be added in a precise, temporally ordered manner. This work informs two decades-old mysteries in the proteasome field, with broader implications for protease biology and multisubunit complex assembly.

A Cross-Sectional View of Fear of Death and Dying Among Skydivers.

The literature lacks a consistent pattern on the relationship between attitudes toward death and dying across occupations and recreational pursuits. The present cross-sectional study categorized a group of individuals engaging in a high-risk recreational activity (i.e., skydivers) on the basis of experience and classified them into student, intermediate, and experts. There were more negative attitudes of death and dying among student skydivers compared with more experienced skydivers. It was also found that expert skydivers had more negative attitudes toward death and dying on some of the measures compared with the intermediate level experienced skydivers. It may be the case that factors such as perceived personal control, overconfidence, and metacognition may be related to these observed differences between the two more experienced groups of skydivers. The possibility of the factors playing a role in skydivers' attitudes toward death and dying should be taken into consideration in the training programs for skydiving.

Characteristics of pornography film actors: self-report versus perceptions of college students.

The assumed characteristics of individuals in the adult entertainment industry have been used to advocate positions for and against pornography. Although prior studies have investigated perceptions of porn actors, no data on the actual characteristics of this group exist. The present study compared the self-reports of 105 male and 177 female porn actors to the perceptions of 399 college students on childhood sexual abuse (CSA), self-esteem, work and non-work sexual behaviors, and safe sex issues. College students were asked to identify the characteristics associated with either a male or female porn star. College students provided underestimates for both female and male porn actors on self-esteem, age of first intercourse, lifetime number of partners outside of work, ideal experience in a romantic partner, concerns regarding sexually transmitted diseases (STDs), enjoyment of sex, and condom use during a first time sexual encounter, but overestimated earnings. Additional differences among male porn stars included an underestimate of the number of partners at work. For female porn stars, college students underestimated their enjoyment of work, the probability of catching an STD, and having unprotected sex. Although there were no significant differences on perceived rates of childhood abuse of porn actors, the incidence of CSA among the porn actor participants were within the ranges of the general population. The majority of college student stereotypes were not supported regarding the perceptions of porn actors. These findings were discussed within the context of attributing unfounded characteristics of individuals to an entire industry.

Pornography actresses: an assessment of the damaged goods hypothesis.

The damaged goods hypothesis posits that female performers in the adult entertainment industry have higher rates of childhood sexual abuse (CSA), psychological problems, and drug use compared to the typical woman. The present study compared the self-reports of 177 porn actresses to a sample of women matched on age, ethnicity, and marital status. Comparisons were conducted on sexual behaviors and attitudes, self-esteem, quality of life, and drug use. Porn actresses were more likely to identify as bisexual, first had sex at an earlier age, had more sexual partners, were more concerned about contracting a sexually transmitted disease (STD), and enjoyed sex more than the matched sample, although there were no differences in incidence of CSA. In terms of psychological characteristics, porn actresses had higher levels of self-esteem, positive feelings, social support, sexual satisfaction, and spirituality compared to the matched group. Last, female performers were more likely to have ever used 10 different types of drugs compared to the comparison group. A discriminant function analysis was able to correctly classify 83% of the participants concerning whether they were a porn actress or member of the matched sample. These findings did not provide support for the damaged goods hypothesis.