Multiple molecular forms of β-galactosidase

Stanley H. Appel, D. H. Alpers, G. M. Tomkins

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


In uninduced lactose-fermenting strains of Escherichia coli, β-galaetosidase migrated as a single rapidly moving eleotrophoretic component which, on sucrose gradient centrifugation, has a sedimentation coefficient of 16 s. On induction, at least 7 eleotrophoretic forms of the enzyme appeared, the slowest of which had a sedimentation coefficient of 34 s. Values for the Michaelis constant of the 16 and 34 s forms were similar. Evidence is presented that this pattern is stable and reproducible in vitro, and reversible in vivo. Nearly identical patterns of galactosidase activity were seen in constitutive bacteria and in various hybrid strains containing an episome derived from E. coli. It is concluded that these forms represent higher molecular weight aggregates of β-galactosidase. A significant portion of the thiogalactoside transacetylase also existed as high molecular weight forms as detected by electrophoresis and density-gradient centrifugation, and could be disaggregated by dialysis or the presence of iso-propyl-β-D-thiogalactoside.

Original languageEnglish (US)
Pages (from-to)12-22
Number of pages11
JournalJournal of Molecular Biology
Issue number1
StatePublished - Jan 1 1965


  • 5,5′dithio-bis-2-nitrobenzoic acid
  • 6-bromo-2-naphthyl-β-D-galactopyranoside
  • BNG
  • DTNB
  • IPTG
  • ONPG
  • TMG
  • acetyl coenzyme A
  • acetyl-CoA
  • i
  • isopropyl-β-D-thiogalactoside
  • orthonitrophenyl-β-D-galactoside
  • the gene controlling inducibility in the lactose operon
  • the structural gene for galactoside permease
  • the structural gene for β-galactosidase
  • thiomethyl-β-D-galactoside
  • y
  • z

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


Dive into the research topics of 'Multiple molecular forms of β-galactosidase'. Together they form a unique fingerprint.

Cite this