Fusion of unilamellar phospholipid vesicles in the presence of proteins and cationic synthetic polypeptides was studied by monitoring the size increase and the mixing of the aqueous contents of the vesicle. It was found that synthetic polypeptides and the proteins known to form 'Molten-globular structure' in acidic media, induced fusion of PS/PE at a molar ratio of 1:1 while other proteins had no effect. Bovine α-lactalbumin, cytochrome c, lysozyme and ribonuclease are found to induce fusion of 1:1 mixture of vesicles containing of phosphotidylserine and phosphotidylethanolamine in the acidic pH. The increase in the initial rate of fusion correlates very well with the conformational change of the protein with decreasing pH from 7 to 2. The structural change of α-lactalbumin in the presence of phospholipid vesicles as a function of pH was followed by using the fluorescence measurements. These phenomenons also parallel with the extent of molten globular structure formation and the extent of binding of α-lactalbumin to the vesicles. These observations, taken together, suggests that the penetration of a hydrophobic segment of α-lactalbumin into the hydrophobic interia of the model membrane causes the fusion of the vesicles. As the ionic strength is increased from 100 mM to 500 mM at pH3, the initial rate of fusion decreased but approached a certain value beyond the ionic strength of 400 mM, suggesting involvement of hydrophobic interactions in fusion mechanism.
Proteins 과 cationic synthetic polypeptides의 존재하에서 단위막의 인지질 막의 융합에 대한 연구는 크기의 변화와 막내의 수용액 성분의 혼합으로 측정하였다.
'Molten-globular structure'를 형성하는 protein 은 산성조건에서 PS:PE (몰 비율 1:1) vesicles 을 융합을 유도하였다. 이런 protein 들은 bovine α-lactalbumin, cytochrome C, lysozyme, 그리고 ribonuclease 이다. 막 융합의 초기 속도의 증가는 pH가 7 에서 2로 감소함에 따라 일어나는 protein의 구조 변화와 밀접한 관련이 있다. 또한 구조 변화는 protein 의 막에 대한 결합량 에도 관계가 있다. α-lactalbumin 에 의한 막 융합 연구에도 hydrophobic interaction 이 존재함을 ionic strength 변화로 알았다. 그래서, 막 융합에는 hydrophobic interaction 이 관여함을 알 수 있었다.
