DNA binding specificities of Escherichia coli Cas1-Cas2 integrase drive its recruitment at the CRISPR locus.

Prokaryotic adaptive immunity relies on the capture of fragments of invader DNA (protospacers) followed by their recombination at a dedicated acceptor DNA locus. This integrative mechanism, called adaptation, needs both Cas1 and Cas2 proteins. Here, we studied in vitro the binding of an Escherichia coli Cas1-Cas2 complex to various protospacer and acceptor DNA molecules.

RNA-binding site of Escherichia coli peptidyl-tRNA hydrolase.

In a cell, peptidyl-tRNA molecules that have prematurely dissociated from ribosomes need to be recycled. This work is achieved by an enzyme called peptidyl-tRNA hydrolase. To characterize the RNA-binding site of Escherichia coli peptidyl-tRNA hydrolase, minimalist substrates inspired from tRNA(His) have been designed and produced.

NMR-based substrate analog docking to Escherichia coli peptidyl-tRNA hydrolase.

Escherichia coli peptidyl-tRNA hydrolase activity is inhibited by 3'-(L-[N,N-diacetyl-lysinyl)amino-3'-deoxyadenosine, a stable mimic of the minimalist substrate 2'(3')-O-(L-[N,N-diacetyl-lysinyl)adenosine. The complex of this mimic with the enzyme has been analyzed by NMR spectroscopy, enabling experimental mapping of the catalytic center for the first time. Chemical shift variations point out the sensitivity of residues Asn10, Met67, Asn68, Gly111, Asn114, Leu116, Lys117, Gly147, Phe148, and Val149 to complex formation.

Detection of biological macromolecules on a biochip dedicated to UV specific absorption.

This work describes an ultraviolet biosensing technique based on specific molecular absorption detected with a previously developed spectrally selective aluminum gallium nitride (AlGaN) based detector. Light absorption signal of DNA and proteins, respectively at 260 nm and 280 nm, is used to image biochips. To allow detection of protein or DNA monolayers at the surface of a biochip, we develop contrast-enhancing multilayer substrates.

Identification in archaea of a novel D-Tyr-tRNATyr deacylase.

Most bacteria and eukarya contain an enzyme capable of specifically hydrolyzing D-aminoacyl-tRNA. Here, the archaea Sulfolobus solfataricus is shown to also contain an enzyme activity capable of recycling misaminoacylated D-Tyr-tRNATyr. N-terminal sequencing of this enzyme identifies open reading frame SS02234 (dtd2), the product of which does not present any sequence homology with the known D-Tyr-tRNATyr deacylases of bacteria or eukaryotes.

Crystal structure at 1.8 A resolution and identification of active site residues of Sulfolobus solfataricus peptidyl-tRNA hydrolase.

The 3-D structure of the peptidyl-tRNA hydrolase from the archaea Sulfolobus solfataricus has been solved at 1.8 A resolution. Homologues of this enzyme are found in archaea and eucarya.

Peptidyl-tRNA hydrolase from Sulfolobus solfataricus.

An enzyme capable of liberating functional tRNA(Lys) from Escherichia coli diacetyl-lysyl-tRNA(Lys) was purified from the archae Sulfolobus solfataricus. Contrasting with the specificity of peptidyl- tRNA hydrolase (PTH) from E.coli, the S.