Fluorescent and radioactive solid phase dideoxy sequencing of pcr products in microtitre plates

Sequence and immunological characterization of a serine-rich antigen from Mycobacterium leprae

Sera from lepromatous leprosy patients were used to screen a Mycobacterium leprae lambda gt11 library. Three positive plaques were picked, and lysogens were constructed. Immunoblot analysis showed that all of the lysogens expressed an apparently identical beta-galactosidase fusion protein which reacted strongly with the sera. The 1.7-kbp insert from one clone was subcloned into the lacZ gene in pUR290; sequence analysis of the end fused to lacZ revealed an open reading frame with no significant homology to previously published sequences. The insert was used to screen an M. leprae cosmid library, and five clones were isolated. The insert was also found to hybridize to clones expressing the M. leprae antigen which had previously been designated class III and 25L. A 1.8-kbp HindIII fragment was subcloned from one of the cosmids and sequenced. The sequence revealed a 1,227-bp open reading frame, encoding a 408-amino-acid protein with a predicted molecular mass of 42,466 Da. The protein contains amino- and carboxy-terminal hydrophobic domains and a hydrophilic central domain; the amino-terminal domain shows some homology to a 51-kDa hypothetical antigen of Mycobacterium tuberculosis, while the hydrophilic region contains a high proportion of serine residues, and we have therefore designated the protein serine-rich antigen (Sra). Some repeated motifs are present in the protein, but their significance is unknown. Seventy-eight percent of serum samples from multibacillary leprosy patients and 68% of serum samples from paucibacillary leprosy patients recognized the fusion protein, showing that this is a major M. leprae antigen. In contrast, all serum samples from endemic controls were negative, while 26% of serum samples from tuberculosis patients were weakly positive.

Carbamoyl phosphate synthetase (CPSase) in the PYR1-3 multigene of Dictyostelium discoideum

We have isolated and sequenced the genomic DNA from the slime-mould Dictyostelium discoideum multi-gene (PYR1-3) encoding the carbamoyl phosphate synthetase II domain (CPSase, EC.6.3.5.5). We describe sequencing by oligo-walking directly on PCR product in the solid-phase, avoiding subcloning procedures. The 2.4 kb fragment completes the sequence of the PYR1-3 gene, has no introns, and has the same structure as the rudimentary gene of Drosophila melanogaster. Comparison with the carbamoyl phosphate synthetases (CPSase I and CPSase II) of other species supports the hypothesis that this gene has arisen by tandem duplication from a smaller common ancestral gene in the progenote.