Crystal structure of an RNA bacteriophage coat protein-operator complex

The RNA bacteriophage MS2 is a convenient model system for the study of protein-RNA interactions. The MS2 coat protein achieves control of two distinct processes--sequence-specific RNA encapsidation and repression of replicase translation--by binding to an RNA stem-loop structure of 19 nucleotides containing the initiation codon of the replicase gene. The binding of a coat protein dimer to this hairpin shuts off synthesis of the viral replicase, switching the viral replication cycle to virion assembly rather than continued replication. The operator fragment alone can trigger self-assembly of the phage capsid at low protein concentrations and a complex of about 90 RNA operator fragments per protein capsid has been described. We report here the crystal structure at 3.0 A resolution of a complex between recombinant MS2 capsids and the 19-nucleotide RNA fragment. It is the first example of a structure at this resolution for a sequence-specific protein-RNA complex apart from the transfer RNA synthetase complexes. The structure shows sequence-specific interactions between conserved residues on the protein and RNA bases essential for binding.     

Ureaplasma urealyticum and chronic lung disease

Neonatal lower respiratory tract colonisation with mycoplasma organisms was examined for an association with chronic lung disease. Ureaplasma urealyticum colonised 9/70 (13%) infants less than 1500 g. Seven (78%) colonised and 33 (54%) non-colonised infants developed chronic lung disease. Logistic regression analyses revealed early gestation, but not mycoplasma colonisation, was independently associated with chronic lung disease.     

Anxiety after a heart attack

An objective measurement of anxiety at defined intervals after the onset of acute cardiac symptoms was made in 203 men admitted to the Coronary Care Unit, Royal Infirmary of Edinburgh, and in 83 patients in a Teesside coronary survey. Of the Teesside patients, 50 were treated at home, 22 were admitted initially to a coronary care unit, and 11 were admitted directly to a general medical ward. In the Edinburgh patients the level of anxiety was high early in the illness, fell rapidly, and rose again towards the end of their stay in hospital. At 4 months it was that of a normal population. After transfer from the coronary care unit the group was not more anxious than other patients in the ward. Reaction to the illness was unrelated to its physical severity. Patients who reacted badly at the beginning were less likely to return to work. The pattern of anxiety in the Teesside patients resembled that of the Edinburgh group, and reaction to illness was largely independent of physical aspects. Treatment in hospital, either through a coronary care unit initially or in a medical ward, did not increase emotional distress. At 3 months patients treated initially in a coronary care unit were less anxious than the others. Throughout the period of study the Teesside patients were more anxious than the Edinburgh patients and outcome was not related to anxiety. Social and environmental differences may account for this.     

Genetically engineered synthesis of precorrin-6x and the complete corrinoid, hydrogenobyrinic acid, an advanced precursor of vitamin B12

BACKGROUND: Genetically engineered synthesis, in which the gene products, cofactors, and substrates of a complete pathway are combined in vitro in a single flask to give the target, can be a viable alternative to conventional chemical construction of molecules of complex structure and stereochemistry. We chose to attempt to synthesize the metal-free corrinoid hydrogenobyrinic acid, an advanced precursor of vitamin B12. RESULTS: Cloning and overexpression of the genes necessary for the S-adenosyl methionine dependent conversion of 5-aminolevulinic acid (ALA) to precorrin-3 and those required for the synthesis of hydrogenobyrinic acid from precorrin-3 completed the repertoire of the 12 biosynthetic enzymes involved in corrin synthesis. Using these enzymes and the necessary cofactors, the multi-enzyme synthesis of hydrogenobyrinic acid from ALA can be achieved in 20% overall yield in a single reaction vessel, corresponding to an average of at least 90% conversion for each of the 17 steps involved. CONCLUSIONS: By replacing the cell wall with glass, and by mixing the soluble biosynthetic enzymes and necessary cofactors, the major segment of the physiological synthesis of vitamin B12 has been accomplished. Since only those enzymes necessary for the synthesis of hydrogenobyrinic acid from ALA are supplied, none of the intermediates is deflected from the direct pathway. This results in an efficiency which in fact surpasses that of nature.