Stoffels Laura, Taunt Henry N, Charalambous Bambos, Purton Saul
Algal Biotechnology Group, Institute of Structural and Molecular Biology, University College London, London, UK.
Research Department of Infection, University College London Medical School, London, UK.
Plant Biotechnol J. 2017 Sep;15(9):1130-1140. doi: 10.1111/pbi.12703. Epub 2017 Mar 7.
There is a pressing need to develop novel antibacterial agents given the widespread antibiotic resistance among pathogenic bacteria and the low specificity of the drugs available. Endolysins are antibacterial proteins that are produced by bacteriophage-infected cells to digest the bacterial cell wall for phage progeny release at the end of the lytic cycle. These highly efficient enzymes show a considerable degree of specificity for the target bacterium of the phage. Furthermore, the emergence of resistance against endolysins appears to be rare as the enzymes have evolved to target molecules in the cell wall that are essential for bacterial viability. Taken together, these factors make recombinant endolysins promising novel antibacterial agents. The chloroplast of the green unicellular alga Chlamydomonas reinhardtii represents an attractive platform for production of therapeutic proteins in general, not least due to the availability of established techniques for foreign gene expression, a lack of endotoxins or potentially infectious agents in the algal host, and low cost of cultivation. The chloroplast is particularly well suited to the production of endolysins as it mimics the native bacterial expression environment of these proteins while being devoid of their cell wall target. In this study, the endolysins Cpl-1 and Pal, specific to the major human pathogen Streptococcus pneumoniae, were produced in the C. reinhardtii chloroplast. The antibacterial activity of cell lysates and the isolated endolysins was demonstrated against different serotypes of S. pneumoniae, including clinical isolates and total recombinant protein yield was quantified at ~1.3 mg/g algal dry weight.
鉴于病原菌中广泛存在的抗生素耐药性以及现有药物的低特异性，开发新型抗菌剂迫在眉睫。内溶素是由噬菌体感染的细胞产生的抗菌蛋白，用于在裂解周期结束时消化细菌细胞壁以释放噬菌体后代。这些高效的酶对噬菌体的靶细菌表现出相当程度的特异性。此外，由于这些酶已进化为靶向细菌细胞壁中对细菌生存至关重要的分子，因此对内溶素产生耐药性的情况似乎很少见。综上所述，这些因素使重组内溶素成为有前景的新型抗菌剂。一般来说，绿色单细胞藻类莱茵衣藻的叶绿体是生产治疗性蛋白质的一个有吸引力的平台，这尤其是因为有成熟的外源基因表达技术，藻类宿主中缺乏内毒素或潜在的感染因子，以及培养成本低。叶绿体特别适合生产内溶素，因为它模拟了这些蛋白质的天然细菌表达环境，同时又没有它们的细胞壁靶点。在这项研究中，对主要人类病原体肺炎链球菌具有特异性的内溶素Cpl-1和Pal在莱茵衣藻叶绿体中产生。细胞裂解物和分离的内溶素对不同血清型的肺炎链球菌（包括临床分离株）表现出抗菌活性，并且总重组蛋白产量定量为约1.3 mg/g藻类干重。
