Nucleotide sequence and transcriptional analysis of the<i>E. coli ush</i>A gene, encoding periplasmic UDP-sugar hydrolase (5'-nucleotidase): regulation of the<i>ushA</i>gene, and the signal sequence of its encoded protein product

Abstract

The DNA sequence of the ushA gene, encoding UDP-sugar hydrolase (5'-nucleotidase), has been determined. The amino-terminal sequence encodes a signal peptide whose predicted processing site is confirmed by N-terminal amino acid analysis of purified mature UshA protein. The signal sequence contains a concentration of rare codons in comparison with the mature sequence. The origins of transcription from the ushA promoter have been determined, using primer extension. Three transcripts, originating within a 6 bp region, were identified and might be related to three overlapping potential -10 hexamers in the ushA promoter region. There was a discernable change in the relative proportion of these transcripts during growth-phase regulation of the ushA gene.