angiogenesis ͉ cancer ͉ progenitor ͉ stem cell ͉ differentiation

PrsA is a peptidyl-prolyl isomerase (PPIase) from Bacillus subtilis belonging to the parvulin family of PPIases. It is a membrane bound lipoprotein at the membrane-wall interface, involved in folding of exported proteins. We present the NMR solution structure of the PPIase domain of PrsA, the first from a Gram-positive bacterium. In addition we mapped out the active site with NMR titration experiments. A high degree of conservation with other members of the parvulin family was revealed in the structure and binding site. Interactions with substrate peptides were also characterized by mutated domains revealing that H122 is indispensable for overall correct folding.

A 45-year-old man needed emergency tracheostomy and cranioplasty. He was intubated with a cuffed oral polyvinylchloride endotracheal tube and ventilated with 100% oxygen before tracheal incision. During opening of the trachea using diathermy, a popping sound was heard and flames originating from the tracheal incision were observed. The endotracheal tube was charred and its lumen had melted. Immediately after the incident, bronchofibroscopic examination revealed inhalation injury. After remaining for 8 weeks in hospital, the patient was transferred to a health care centre, where he was found dead in his bed.

LETTERReply to Kerbel et al.: EPCs are again claimed to be essential in yet other models despite the irreproducibility of the original experiments introducing themWe conducted a study in which evidence for the existence of bone marrow (BM)-derived EPCs was not found in multiple physiologically relevant settings including cancer growth, suggesting such cells to be artifactual rather than physiological (1).Kerbel et al. EPCs seem elusive, moving targets, impossible to verify in carefully controlled experiments but always proposed to emerge in yet another specific model (5) or in another disguise. We did not observe such cells in a variety of highly relevant, sophisticated in vivo experiments. We also were not able to reproduce original findings introducing EPCs (6-8).