Expression and identification of the strA-strB gene pair from streptomycin-resistant Erwinia amylovora

Gene. 1995 Jan 11;152(1):47-51. doi: 10.1016/0378-1119(94)00721-4.


Deletions in either of the genes in the strA-strB gene pair of Erwinia amylovora plasmid pEa34 resulted in a dramatic decrease in streptomycin resistance (SmR), but SmR was restored to high levels by complementation. When strA and strB were cloned separately on a lacIq/Ptac-based expression vector in Escherichia coli, only the protein encoded by strA was produced. When a strong Shine-Dalgarno sequence was introduced and the start codon was located outside the double-stranded region of the stable stem-loop, the protein encoded by strB was produced. Biochemical analysis of the respective phosphorylated products demonstrated that strA and strB encoded aminoglycoside-3"-phosphotransferase (APH(3")-Ib) and aminoglycoside-6-phosphotransferase (APH(6)-Id), respectively. These data suggest that the high-level SmR in bacteria containing strA and strB is due to the combined action of the two enzymes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • Cloning, Molecular
  • DNA Mutational Analysis
  • Drug Resistance, Microbial
  • Erwinia / drug effects
  • Erwinia / genetics*
  • Escherichia coli / genetics
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial / genetics*
  • Molecular Sequence Data
  • Phosphotransferases (Alcohol Group Acceptor) / genetics*
  • RNA, Messenger / genetics
  • Regulatory Sequences, Nucleic Acid / genetics
  • Streptomycin / pharmacology*


  • RNA, Messenger
  • Phosphotransferases (Alcohol Group Acceptor)
  • streptomycin 6-kinase
  • streptomycin 3''-kinase
  • Streptomycin