Purification and characterization of a membrane-associated testosterone-binding protein from Pseudomonas testosteroni

Can J Biochem Cell Biol. 1983 May;61(5):307-12. doi: 10.1139/o83-042.

Abstract

A steroid-binding protein, identified in the supernatant generated when membrane vesicles of Pseudomonas testosteroni are produced and harvested by centrifugation, has been purified 49-fold to homogeneity. It has a molecular weight of 30 000-35 000 and it specifically binds the C19 steroids dihydrotestosterone, testosterone, and androstenedione. It is a basic protein with an isoelectric point at pH 7.3. Binding of testosterone exhibited normal saturation kinetics with an affinity constant, Kd, of 3.9 X 10(-8) M. Binding was inhibited by divalent cations, but the sulfhydryl reagents dithiothreitol and mercaptoethanol did not affect activity. It is suggested that this and other membrane-associated steroid-binding proteins concentrate the steroid at the membrane surface before it is transported into the cytoplasm of P. testosteroni.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / analysis
  • Androgen-Binding Protein / isolation & purification
  • Androgen-Binding Protein / metabolism*
  • Binding, Competitive
  • Carrier Proteins / metabolism*
  • Cell Membrane / metabolism
  • Kinetics
  • Molecular Weight
  • Pseudomonas / metabolism*
  • Testosterone / metabolism*

Substances

  • Amino Acids
  • Androgen-Binding Protein
  • Carrier Proteins
  • Testosterone