xcLeigh

Contributions

BBa_I732005: Description of the structure of E.coli beta-galactosidase

The β-galactosidase tetramer (Fig. 1) is comprised of four polypeptide chains, labeled A–D, each of 1023 amino acids.[1] Each 1023-amino-acid monomer is made up of five domains, 1–5, which are respectively colored blue, green, yellow, cyan and red in Fig. 1. Domain 3 has an α/β or ‘TIM’ barrel structure with the active site located at the C-terminal end of the barrel.[2] Both Mg2+ and Na+ are required for maximal activity of β-galactosidase.[3]

Fig.1 | View of the β-galactosidase tetramer looking down one of the two-fold axes. Coloring is by domain: complementation peptide, orange; Domain 1, blue; Domain 2, green; Domain 3, yellow; Domain 4, cyan; Domain 5, red. Lighter and darker shades of a given color are used to distinguish the same domain in different subunits. The metal cations in each of the four active sites are shown as spheres: Na+, green; Mg++, blue. [2]

BBa_K3196036: Advantages of AOX1 promoter

AOX1 promoter is highly repressed in cells grown on glucose, glycerol, and most other carbon sources, but it is strongly induced by methanol.[4-7] Expression of AOX1 is tightly regulated at the transcriptional level [8] and appears to be controlled by both repression/derepression and induction mechanisms (Fig. 2).[9]

Fig.2 | Specific AOX activity during the transition phase in four P. pastoris high cell density fed-batch cultivations.[9]