The structure of a polyketide synthase bimodule core.

Polyketide synthases (PKSs) are predominantly microbial biosynthetic enzymes. They assemble highly potent bioactive natural products from simple carboxylic acid precursors. The most versatile families of PKSs are organized as assembly lines of functional modules. Each module performs one round of precursor extension and optional modification, followed by directed transfer of the intermediate to the next module. While enzymatic domains and even modules of PKSs are well understood, the higher-order modular architecture of PKS assembly lines remains elusive. Here, we visualize a PKS bimodule core using cryo-electron microscopy and resolve a two-dimensional meshwork of the bimodule core formed by homotypic interactions between modules. The sheet-like organization provides the framework for efficient substrate transfer and for sequestration of trans-acting enzymes required for polyketide production.

Depressive symptoms among teenagers in the emergency department: prevalence estimate and concordance with parental perceptions.

PURPOSE: This study aims to estimate the prevalence of depressive symptoms among adolescents seen in hospital emergency departments and to investigate the concordance between self-reported adolescent depression and parental perceptions of their adolescents' health status. METHOD: A multicentre cross-sectional survey in three emergency departments receiving adolescents in Ile-de-France took place in 2010. All adolescents completed a questionnaire including the Adolescent Depression Rating Scale (ADRS) and a series of questions concerning somatisation and risk behaviours. Parents simultaneously completed a questionnaire collecting their perceptions of their adolescent's health status. RESULTS: The study included 346 adolescents, and of them, 320 were fully analysed. ADRS scores were in the normal range for 70.6 % of the sample (score of <3) (n=226); 19.4 % (n=62) showed moderate depressive symptoms (3 ≤ score<6), and 10.0 %, severe depressive symptoms (score of ≥ 6) (n=32). We observed a wide discrepancy between adolescent depression, determined by a score on a self-administered scale, and parental perceptions of it. CONCLUSION: Routine use of a self-administered questionnaire in emergency units could enable identification of adolescents with moderate or severe depressive symptoms. The present study confirms the importance of increasing parental awareness of their adolescent children's depressive symptoms.