Protein splicing of the three Pyrococcus abyssi ribonucleotide reductase inteins.

An intein is a polypeptide that interrupts the functional domains of a protein, called the exteins. The intein can facilitate its own excision from the exteins, concomitant with the ligation of the exteins, in a process called protein splicing. The alpha subunit of the ribonucleotide reductase of the extreme thermophile Pyrococcus abyssi is interrupted by three inteins in separate insertion sites. Each intein can facilitate protein splicing when over-expressed in Escherichia coli, with affinity domains serving as the exteins. The influence of the N-terminal flanking residue on the efficiency of splicing is specific to each intein. Each intein has a different downstream nucleophilic residue, and cannot tolerate substitution to a residue of lesser or equal nucleophilicity. The influence of the conserved penultimate His also differs between the inteins.

A scalable, fully automated process for construction of sequence-ready barcoded libraries for 454.

We present an automated, high throughput library construction process for 454 technology. Sample handling errors and cross-contamination are minimized via end-to-end barcoding of plasticware, along with molecular DNA barcoding of constructs. Automation-friendly magnetic bead-based size selection and cleanup steps have been devised, eliminating major bottlenecks and significant sources of error. Using this methodology, one technician can create 96 sequence-ready 454 libraries in 2 days, a dramatic improvement over the standard method.