호박벌 유래 디펜신의 전체 아미노산 서열의 구조 분석 후에 항균활성을 갖는 서열을 선발하였고, 전체 및 펩타이드 길이와 구조적 차이에 대한 종합적인 결과로서 기존에 보고되어진 ${alpha}$-helix 구조의 펩타이드 보다는 ${eta}$-sheet의 일부 서열과 ${alpha}$-helix의 서열이 공존할 때 항균 활성이 보다 뛰어남을 확인하였다. 특히 시스테인-아르기닌 (38C-39R)이 포함되어 있는 펩타이드 서열에서 항균력이 우수하였고, 이는 세포벽에 친화력이 있는 염기성 펩타이드의 특성으로 예상하고 있다.
Antimicrobial peptides of insects are found and reported as immune defence system against infectious agents. The peptides are produced by fat body cells and thrombocytoids, a blood cell type. Defensin is 38-45 amino acids long and consists of an ${alpha}$-helix linked by a loop to an antiparallel ${eta}$-sheet. Defensin from a bumblebee, Bombus ignitus, is known to comprise 52 amino acid residues. This peptide consists of two ${alpha}$-helixes; ACAANCLSM and KTNFKDLWDKRF and one ${eta}$-sheet; GGRCENGVCLCR. We carried out antibacterial activity test by radial diffusion assay against Staphylococcus aureus (Gram positive), Escherichia coli (Gram negative), Pseudomonas syringae (Gram negative), Candida albicans (fungi), MDRPA, MRSA, and VRE (antimicrobial resistant microbes) with synthetic oligopeptides from Peptron (Daejeon, Korea). The predicted curtailment fragment (GGRCEVCLCR-$NH_2$) for ${eta}$-sheet had strong antibacterial activity when internal amino acids were removed. But, curtailment fragments (ACAANCLSM-$NH_2$ and TNFKDLWDKR-$NH_2$) of ${alpha}$-helix were not showed antibacterial activity. These synthetic oligopeptides were showed the great activity against Gram positive and negative bacteria.
