Nucleotide sequence of a gene, hpt, for hypoxanthine phosphoribosyltransferase from Vibrio harveyi.

In the process of sequencing the region of Vibrio harveyi DNA containing the luxR gene (1), which encodes an activator of luminescence gene transcription, another large open reading frame was also sequenced. This coding region is 528 base pairs in length, is located immediately upstream from the luxR gene and is transcribed in the opposite direction (fig. 1). The deduced 176 amino acid sequence was used to search the Protein Identification Resource's database using the University of Wisconsin's Genetics Computer Group's set of sequence analysis programs (2). This comparison revealed a significant amount of similarity to several mammalian hypoxanthine-guanine phosphoribosyltransferase enzymes. For example, a 174 amino acid sequence in the open reading frame had 64% similarity and 39% identity with human HGPRT (3) (fig. 2). Two mutated recombinant cosmids containing different Tn5 insertions, pRS215(luxR::Tn5) and pRS238(hpt::Tn5), were used to transform two E. coli strains, GP120 (purEtlpro-gpt-lac) (4) and S0609 (ara tlpro-gpt-lac thi hpt purD deoD rpsL) (5). Strain GP120 cannot grow on minimal medium supplemented with guanine as a purine source. The transformants in this strain were unable to grow on this medium indicating that complementation of the gpt defect had not occurred. Strain S0609 cannot grow on minimal media supplemented with guanine or hypoxanthine as purine sources. Transformants in this strain containing pRS215 grew well on hypoxanthine minimal medium, but transformants containing pRS238 could not grow indicating that the cloned gene encoded by the open reading frame could complement the hpt defect. We conclude that we have cloned and sequenced an hpt gene from V. harveyi.