Difference between revisions of "Beta-galactosidase"

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*You can measure lacZ activity using flow cytometry.  See [http://www.cyto.purdue.edu/flowcyt/research/micrflow/jepras/jepras2.htm A flow cytometric study of stationary phase gene expression in E.coli using lacZ reporter gene fusion]
 
*You can measure lacZ activity using flow cytometry.  See [http://www.cyto.purdue.edu/flowcyt/research/micrflow/jepras/jepras2.htm A flow cytometric study of stationary phase gene expression in E.coli using lacZ reporter gene fusion]
 
**This paper uses [http://probes.invitrogen.com/media/pis/mp02904.pdf C<sub>12</sub>FDG] from Invitrogen.  However, FDG might be a better substrate in gram-negative bacteria like ''Escherichia coli'' <cite>Plovins-ApplEnvironMicrobio-1994</cite>
 
**This paper uses [http://probes.invitrogen.com/media/pis/mp02904.pdf C<sub>12</sub>FDG] from Invitrogen.  However, FDG might be a better substrate in gram-negative bacteria like ''Escherichia coli'' <cite>Plovins-ApplEnvironMicrobio-1994</cite>
*Alpha-complementation of &beta;-galactosidase does not seem to yield activities equal to wildtype &beta;-galactosidase. Depending on the fragment, the activity can be up to 24% of wildtype <cite>Zamenhof-JBacteriol-1972</cite>.  (If anyone has a better reference comparing results from a Miller assay of alpha-complementated &beta;-galactosidase with wildtype, please include it here.)
+
*Alpha-complementation of &beta;-galactosidase does not seem to yield activities equal to wildtype &beta;-galactosidase. Depending on the fragment, the activity can be up to 24% of wildtype <cite>Zamenhof-JBacteriol-1972</cite>.  '''(If anyone has a better reference comparing results from a Miller assay of alpha-complementated &beta;-galactosidase with wildtype, please include it here.)'''
  
 
==Protocols==
 
==Protocols==

Revision as of 13:49, 18 October 2007

Some interesting facts [1]

  • A tetramer of 4 identical subunits
  • Each subunit is 120kD.
  • Active only as a tetramer.
  • Mutations in some of the codons of the N-terminal 60aa or C-terminal 100aa results in an inactive, dimeric β-galactosidase. [2]
  • If the above sequences are deleted, the missing protein fragment can be replaced by the corresponding peptide. This is called intracistronic alpha or omega complementation respectively.
  • Its N-terminal 23 residues can be replaced by any amino acid residues without affecting the enzymatic activity.
  • A mutant with an internal deletion of codons 21-41 of the lacZ gene does not produce any active β-galactosidase.
  • A mutant with a deletion of everything past residue 60 (i.e. it expresses only the first 60 N-terminal amino acids) does not produce any active β-galactosidase.
  • You can measure lacZ activity using flow cytometry. See A flow cytometric study of stationary phase gene expression in E.coli using lacZ reporter gene fusion
    • This paper uses C12FDG from Invitrogen. However, FDG might be a better substrate in gram-negative bacteria like Escherichia coli [3]
  • Alpha-complementation of β-galactosidase does not seem to yield activities equal to wildtype β-galactosidase. Depending on the fragment, the activity can be up to 24% of wildtype [4]. (If anyone has a better reference comparing results from a Miller assay of alpha-complementated β-galactosidase with wildtype, please include it here.)

Protocols

  1. Beta-Galactosidase Assay (A better Miller)
  2. BE.109:Protein engineering/Assessing beta-galactosidase

Reference

  1. ISBN:3-11-014830-7 [Muller-Hill-1996]
  2. ISBN:0317118099 [Beckwith-1970]
  3. Plovins A, Alvarez AM, Ibañez M, Molina M, and Nombela C. Use of fluorescein-di-beta-D-galactopyranoside (FDG) and C12-FDG as substrates for beta-galactosidase detection by flow cytometry in animal, bacterial, and yeast cells. Appl Environ Microbiol. 1994 Dec;60(12):4638-41. PubMed ID:7811104 | HubMed [Plovins-ApplEnvironMicrobio-1994]
  4. Zamenhof PJ and Villarejo M. Construction and properties of Escherichia coli strains exhibiting -complementation of -galactosidase fragments in vivo. J Bacteriol. 1972 Apr;110(1):171-8. PubMed ID:4552986 | HubMed [Zamenhof-JBacteriol-1972]
  5. Ullmann A. Complementation in beta-galactosidase: from protein structure to genetic engineering. Bioessays. 1992 Mar;14(3):201-5. DOI:10.1002/bies.950140311 | PubMed ID:1345751 | HubMed [Ullmann-Bioessays-1992]
  6. [by] Jeffrey H. Miller. Experiments in molecular genetics. [Cold Spring Harbor, N.Y.] Cold Spring Harbor Laboratory, 1972. ISBN:0879691069 [Miller-1972]
    original β-galactosidase assay by Miller
All Medline abstracts: PubMed | HubMed