Woźnica Wioleta M, Bigos Joanna, Łobocka Małgorzata B
Zakład Biochemii Drobnoustrojów, Instytut Biochemii i Biofizyki Polskiej Akademii Nauk, Warszawa; Samodzielny Zakład Biologii Mikroorganizmów, Wydział Rolnictwa i Biologii SGGW, Warszawa.
Instytut Uprawy Nawożenia i Gleboznawstwa, Państwowy Instytut Badawczy, Puławy; Instytut Uprawy Nawożenia i Gleboznawstwa, Państwowy Instytut Badawczy, Puławy.
Postepy Hig Med Dosw (Online). 2015 Jan 23;69:114-26.
The release of phage progeny from an infected bacterium is necessary for the spread of infection. Only helical phages are secreted from a cell without causing its destruction. The release of remaining phages is correlated with bacterial lysis and death. Thus, the understanding of phage lytic functions is crucial for their use in the fight with bacterial pathogens. Bacteriophages with small RNA or DNA genomes encode single proteins which are called amurins and cause lysis by the inhibition of cell wall synthesis. Bacteriophages of double-stranded DNA genomes, which dominate in the environment, encode enzymes that are called endolysins and contribute to lysis by the cleavage of cell wall peptydoglycan. Endolysins that do not contain signal sequences cannot pass the cytoplasmic membrane by themselves. Their access to peptidoglycan is provided by membrane proteins - holins, which can form in the membrane large pores, that are called "holes". Some endolysins do not require holins for their transport, owing to the presence of the so called SAR sequence at their N-terminus. It enables their transport through the membrane by the bacterial sec system. However, it is not cleaved off, and thus these endolysins remain trapped in the membrane in an inactive form. Their release, which is correlated with the activation, occurs as a result of membrane depolarization and depends on proteins that are called pinholins. Pinholins form in membrane pores that are too small for the passage of endolysins but sufficient for membrane depolarization. Proteins that are called antiholins regulate the timing of lysis, through the blockage of holins action until the end of phage morphogenesis. Additionally, newly identified lytic proteins, spanins, participate in the release of progeny phages from Gram-negative bacteria cells. They cause the destruction of outer cell membrane by its spanning with the cytoplasmic membrane. This is possible after the endolysin-mediated destruction of peptidoglycan, which separates both membranes, and ensures the fast completion of lysis.
噬菌体后代从受感染细菌中释放出来对于感染的传播至关重要。只有螺旋状噬菌体可以从细胞中分泌出来而不导致细胞破坏。其余噬菌体的释放与细菌裂解和死亡相关。因此，了解噬菌体的裂解功能对于其用于对抗细菌病原体至关重要。具有小RNA或DNA基因组的噬菌体编码单一蛋白质，称为阿穆林蛋白，通过抑制细胞壁合成导致裂解。在环境中占主导地位的双链DNA基因组噬菌体编码称为内溶素的酶，通过裂解细胞壁肽聚糖促进裂解。不含信号序列的内溶素自身无法穿过细胞质膜。膜蛋白——孔蛋白为它们接近肽聚糖提供了途径，孔蛋白可在膜中形成称为“孔”的大孔。一些内溶素由于其N端存在所谓的SAR序列，不需要孔蛋白来运输。这使得它们能够通过细菌的sec系统穿过膜。然而，它不会被切割掉，因此这些内溶素以无活性形式被困在膜中。它们的释放与激活相关，是膜去极化的结果，并且取决于称为微小孔蛋白的蛋白质。微小孔蛋白在对于内溶素通过来说太小但足以导致膜去极化的膜孔中形成。称为抗孔蛋白的蛋白质通过阻断孔蛋白的作用直到噬菌体形态发生结束来调节裂解的时间。此外，新发现的裂解蛋白——跨膜蛋白，参与子代噬菌体从革兰氏阴性细菌细胞中的释放。它们通过将外细胞膜与细胞质膜连接起来导致外细胞膜的破坏。这在内溶素介导的肽聚糖破坏之后是可能的，肽聚糖破坏会使两层膜分离，并确保裂解快速完成。
