Part:BBa_K1531004

Bovine beta casein (B variant) with full alpha-factor yeast secretion signal

Beta casein is one of four major caseins (cheese proteins) found in bovine cheese. Together with Kappa casein, it is necessary and sufficient to create casein micelles.

At least 12 different genetic variants of bovine Beta casein have been identified and characterized. The B allele used here is associated with improved milk coagulation.

The coding sequence for this gene is preceded by a secretion signal derived from the yeast mating pheromone alpha-factor in Saccharomyces cerevisiae, facilitates secretion of heterologous proteins in yeast. We used a full length form of the full alpha-factor protein with kex and ste13 protease cleavage sites (FAKS). (www.pnas.org/content/81/15/4642.short). In addition, the entire construct is flanked by SapI restriction sites, for cloning into DNA2.0's Electra system.

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BJ101HS 2020

Figure 1.

β-casein(β-CN) is a protein which could self-associate as a macroscopic flocculent emulsion. The condition that promotes the self-association process is adjustable. In a newly published paper we cited below, researchers found that both temperature (5–55 °C) and divalent cation addition (Ca2+ or Mg2+) can have influence on β-CN-stabilized emulsions and this influence is reversible. The detailed method is to measure the particle size of 0.5% (w/w) β-CN in 10 mM imidazole/HCl buffer (pH 6.8), in a condition of adjusting temperature and divalent cations. The result shows that Ca2+ has a stronger force to promote the formation of emulsion. Furthermore, β-CN/Ca flocculated after incubation at 55 °C for 20 min and displayed significantly different physical properties compared to emulsions in β-CN solution or β-CN/Mg solution when temperature ranged from 5–55°C. This phenomenon is attributed to the interaction of adsorbed β-CN between droplets and the interaction of adsorbed and non-adsorbed β-CN aggregates in the aqueous phase via calcium bridges. Based on this paper, we could predict the self-association process and adjust the feature of β-casein.

[1] Li, M. , O'Mahony, J. A. , Kelly, A. L. , & André Brodkorb. (2019). The influence of temperature- and divalent-cation-mediated aggregation of β-casein on the physical and microstructural properties of β-casein-stabilised emulsions. Colloids and surfaces B: Biointerfaces, 187, 110620.

（Added by BJ101HS）

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal XhoI site found at 252
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal SapI site found at 1
  Illegal SapI.rc site found at 910