Part:BBa_K2278022

Lecrocin I antimicrobial peptide with Alpha-Factor Secretion Signal

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 244
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]

Introduction

This DNA biobrick was designed in order to produce Lecrocin I AMP in a yeast organism strain.

1- Biological background

Mechanisme Antimicrobial peptides are phylogenitically ancient components of innate defense mechanisms of both invertebrates and vertebrates. In the context of growing prevalence of antibiotic-resistance of bacterial strain, the AMP can be considered as potential new therapeutical candidates. Leucrocin I from Siamese crocodile white blood cells shows a good antibacterial activity towards Vibrio cholerae. The peptide is a 7 amino acid residue : NGVQPKY with a molecular mass around 806.99 Da. The mechanism of action of the Leucrocin I has been observed with fluorescence and electron microscopy This cationic molecules and can target bacterium membranes, to create pores in it, leading to the lysis of the cells.

Figure 1: Scanning electron micrographs of Vibrio cholerae treated with peptides (a) control control bacteria c) bacteria treated with AMPs (Yaraksa and al., 2014)

2- Usage in iGEM projects

The part was designed to constitutively produce the leucrocin I AMP with a yeast promoter. The α-factor (BBa_K1800001) sequence contains a RBS and a signal sequence to secrete the produced peptides.

Experiments

1- Molecular biology

The gene was placed in silico under the control of an alpha factor signal. IDT performed the DNA synthesis and delivered the part as gBlock.  The construct was cloned by conventional ligation into pSB1C3 plasmid The construction was then inserted on plasmid pPICZa and integrated in the yeast genome.

Analysis of the restriction map

Figure 2: Analysis of the restriction map BBa_K2278022 in pSB1C3. Digested plasmids are electrophoresed through an 0.7% agarose gel. The desired plasmids lengths are pSB1C3 (2029bp) the other band correspond to a 300bp insert.

Sequencing

Figure 3: Sequencing of pSB1C3+ BBa_K2278022 1500 ng of plasmid are sequenced. 1 oligo was used to perform the sequencing. The obtained sequence were blast on the BBa_K2278022 sequence with the iGEM sequencing online tools.

The sequencing successfully validated the sequence of the biobrick.

2- Expression in vivo

Integration in Pichia pastori genome

Protocole

The biobrick was placed in silico under the control of p(GAP) promoter (BBa_K431009) and was cloned in pPICZalpha vector, a good expression vector for Pichia pastoris. The plasmid was then linearized and transferred in Pichia pastoris by electroporation. The integration is predicted to be at the p(GAP) location. Indeed, the p(GAP) promoter makes genome recombination easier in Pichia pastoris genome thanks to its homology site.

Figure 3: Integration of p(GAP)+BBa_K2278022 in pichia pastoris To verify the function of the new Biobrick, we performed a DNA extraction. To check the length of the resulting DNA, we digested the DNA with EcoRI and Ncos restriction enzyme and electrophoresed the reactions through an 0,7% agarose gel. Lane 1 correspond to 1kb DNA ladder (new England bolas, Inc)

Expression of Leucrocin I AMP

Leucrocin I production was performed with the P. pastoris YPD 40 g/L glucose and grown for 4 days at 30 °C in an agitating incubator. 15mL of each supernatant culture were stored at 4°C while 35mL were freeze-dried and then resuspended in 3.5mL of water.

Characterization

Toxicity assay

The engineered yeast were used in a halo assay against V. harveyi as the target of AMPs. A paper soacked with a yeast solution was placed on the plate and V. harveyi growth in the viscinity of the yeast patch was followed. The toxicity assay did not reveal any activity of the Leucrocin I AMP