Ubiquitin‐specific protease‐like 1 (USPL1) is a SUMO isopeptidase with essential,non‐catalytic functions

Isopeptidases are essential regulators of protein ubiquitination and sumoylation. However, only two families of SUMO isopeptidases are at present known. Here, we report an activity‐based search with the suicide inhibitor haemagglutinin (HA)‐SUMO‐vinylmethylester that led to the identification of a surprising new SUMO protease, ubiquitin‐specific protease‐like 1 (USPL1). Indeed, USPL1 neither binds nor cleaves ubiquitin, but is a potent SUMO isopeptidase both in vitro and in cells. C13orf22l—an essential but distant zebrafish homologue of USPL1—also acts on SUMO, indicating functional conservation. We have identified invariant USPL1 residues required for SUMO binding and cleavage. USPL1 is a low‐abundance protein that colocalizes with coilin in Cajal bodies. Its depletion does not affect global sumoylation, but causes striking coilin mislocalization and impairs cell proliferation, functions that are not dependent on USPL1 catalytic activity. Thus, USPL1 represents a third type of SUMO protease, with essential functions in Cajal body biology.     

Diel changes in DDT absorption and breakdown rates and respiratory rhythm in the housefly, Musca domestica

Absorption rates in three strains of housefly show little variation when DDT is applied at different times during the 24-hr cycle. Rates of breakdown of DDT to DDE, however, vary significantly at different times of the day with most rapid breakdown at 05.00–05.30 and 15.00 hr, corresponding to diel peaks in oxygen consumption. The pre-dawn peak breakdown rates occur at the times at which the flies were found, previously, to be most susceptible to DDT, thus this change in susceptibility must have other causes.

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Zusammenfassung Die Geschwindigkeit, mit der DDT von drei Stubenfliegenrassen absorbiert wurde, zeigte nur wenig Verschiedenheit, wenn es zu verschiedenen Zeiten im Verlauf des 24-h-Tages appliziert wurde. Die Rate des Abbaus von DDT zu DDE variierte dagegen im Lauf des Tages, sie war am grössten um 5.00 bis 5.30 Uhr und um 15.00 Uhr, entsprechend den Tagesspitzen des Sauerstoff-Verbrauchs. Das erste Abbaumaximum (vor Tagesanbruch) fiel zusammen mit der Zeit, in der die Fliegen höchste Empfindlichkeit gegenüber DDT zeigten (vgl. vorige Veröffentlichung). Diese tageszeitspezifische Empfindlichkeit liess sich demnach keineswegs mit einer (geringeren) Abbaugeschwindigkeit in Zusammenhang bringen.

     

Structural understanding of stabilization patterns in engineered bispecific Ig‐like antibody molecules

Bispecific immunoglobulin‐like antibodies capable of engaging multiple antigens represent a promising new class of therapeutic agents. Engineering of these molecules requires optimization of the molecular properties of one of the domain components. Here, we present a detailed crystallographic and computational characterization of the stabilization patterns in the lymphotoxin‐beta receptor (LTβR) binding Fv domain of an anti‐LTβR/anti‐TNF‐related apoptosis inducing ligand receptor‐2 (TRAIL‐R2) bispecific immunoglobulin‐like antibody. We further describe a new hierarchical structure‐guided approach toward engineering of antibody‐like molecules to enhance their thermal and chemical stability. Proteins 2009. © 2009 Wiley‐Liss, Inc.     

Chemical strategies for functional proteomics

With complete genome sequences now available for several prokaryotic and eukaryotic organisms, biological researchers are charged with the task of assigning molecular and cellular functions to thousands of predicted gene products. To address this problem, the field of proteomics seeks to develop and apply methods for the global analysis of protein expression and protein function. Here we review a promising new class of proteomic strategies that utilizes synthetic chemistry to create tools and assays for the characterization of protein samples of high complexity. These approaches include the development of chemical affinity tags to measure the relative expression level and post-translational modification state of proteins in cell and tissue proteomes. Additionally, we discuss the emerging field of activity-based protein profiling, which aims to synthesize and apply small molecule probes that monitor dynamics in protein function in complex proteomes.