Beta-galactosidase

(Difference between revisions)

Revision as of 18:02, 8 November 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.)

All Medline abstracts: PubMed HubMed

@@ Line 27: / Line 27: @@
 #Zamenhof-JBacteriol-1972 pmid=4552986
 #Thibodeau-Biotechniques-2004 pmid=15038156
+#WorthingtonBiochem http://www.worthington-biochem.com/BG/default.html
 </biblio>
 [[Category:Material]] [[Category:Enzyme]] [[Category:Reporter]]