en زیست شناسی ملکولی Molecular Biology مقالات اصلی Original Article <div style="text-align: justify;"><strong><em>Background:</em></strong> Antimicrobial peptides belong to the innate defence system of creatures. These peptides&nbsp;attach to the bacterial membrane in order to die microorganisms by penetrating them. Hence, biotechnology&nbsp;researchers pay more attention to produce antimicrobial peptides for use in various fields. The studies&nbsp;showed that rabbit tissue with inflammation and skin ulcers would be producing CAP18 peptide, which&nbsp;belongs to the cathelicidin group.<br> <br> <strong><em>Methods:</em></strong> In this study, the optimized sequence of the cap18 gene was placed into the pPICZA&alpha; plasmid&nbsp;after the alpha-factor signal and transformed into Pichia pastoris (X-33 strain). Purification of the&nbsp;recombinant peptide was done based on its histidine tail at C-terminal, and western blotting method was<br> used to demonstrate the purification of rCAP18. The antibacterial activity of the purified and desalted&nbsp;rCAP18 was investigated at different concentrations against pathogenic bacteria.<br> <br> <strong><em>Results:</em></strong> The maximum expression level of rCAP18 (17.5 kDa) was seen 90 h after induction of alcohol&nbsp;oxidase I (AOX1) promoter with methanol. The concentration of rCAP18 was 33 mg/L after purification&nbsp;with Ni-NTA Sepharose column. The function of rCAP18 (4.3, 5.7, 7 &mu;g/ml) was investigated<br> against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Results showed that&nbsp;%CFU/cm2 reached 28% after P. aeruginosa cells treatment with 7 &mu;g/ml of rCAP18.<br> <br> <strong><em>Conclusions:</em></strong> This study presented the findings related to heterologous expression of cap18 gene, and&nbsp;evaluation of rCAP18 antibacterial effects. Our results showed that rCAP18 plays a significant role in&nbsp;inhibiting bacterial growth, especially Gram-negative bacteria.</div> Antibacterial activity, Cathelicidin, Recombinant CAP18, Heterologous expression. 622 632 http://rbmb.net/browse.php?a_code=A-10-733-1&slc_lang=en&sid=1 Mahla Nikpoor 100319475328460012456 100319475328460012456 No Department of Agricultural Biotechnology, Shahid Bahonar University of Kerman, Kerman, Iran. Azadeh Lohrasbi-Nejad a.lohrasbi@uk.ac.ir 100319475328460012457 100319475328460012457 Yes Department of Agricultural Biotechnology, Shahid Bahonar University of Kerman, Kerman, Iran. Jafar Zolala 100319475328460012458 100319475328460012458 No Department of Agricultural Biotechnology, Shahid Bahonar University of Kerman, Kerman, Iran.