Xu Chen1, Jinhong Wu2, Fujia Yang3, Mi Zhou2, Ruibin Wang4, Jianlian Huang5, Yuzhi Rong6, Jianhua Liu7, Shaoyun Wang8. 1. School of Mechanical Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China. 2. Department of Food Science and Engineering, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China. 3. College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China. 4. Instrumental Analysis Center, Shanghai Jiao Tong University, Shanghai 200240, China. 5. Key Laboratory of Refrigeration and Conditioning Aquatic Products Processing of Ministry of Agriculture and Rural Affairs, Xiamen 361022, China. 6. School of Perfume and Aroma Technology, Shanghai Institute of Technology, Shanghai 201418, China. 7. International Faculty of Applied Technology, Yibin University, Yibin, Sichuan 644000, China. 8. College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China. Electronic address: shywang@fzu.edu.cn.
Abstract
INTRODUCTION: Antifreeze peptides regulate the physiological functions of frozen cells and even their apoptosis; however, the mechanisms by which antifreeze peptides regulate these processes remain unclear, although the interactions between cell membranes and ice are well known to be important in this process. OBJECTIVES: Our study aims to investigate how antifreeze peptides regulate cell physiological functions during the freezing process. METHODS: We investigated the cryoprotective effect of rsfAFP on the physiological functions of S. thermophilus under freezing stress by measuring cellular metabolism activity, intracellular enzyme activity, cell membrane characterization, and cell apoptosis. The mechanism by which rsfAFP impacts S. thermophilus physiological functions under freezing stress was investigated using multispectral techniques and cryo-TEM. RESULTS: We show that a recombinant antifreeze peptide (rsfAFP) interacts with the extracellular capsular polysaccharides and peptidoglycan of Streptococcus thermophilus and ice to cover the outer layer of the membrane, forming a dense protective layer that regulates the molecular structure of extracellular ice crystals, which results in reduced extracellular membrane damage, depressed apoptosis and increased intracellular metabolic activity. This interaction mechanism was indicated by the fact that S. thermophilus better maintained its permeability barrier, membrane fluidity, membrane structural integrity, and cytoplasmic membrane potential during freezing stress with rsfAFP treatment. CONCLUSION: These results provide new insights into the mechanism by which rsfAFP regulates frozen cellphysiological functionsand apoptosis under freezing stress.
INTRODUCTION: Antifreeze peptides regulate the physiological functions of frozen cells and even their apoptosis; however, the mechanisms by which antifreeze peptides regulate these processes remain unclear, although the interactions between cell membranes and ice are well known to be important in this process. OBJECTIVES: Our study aims to investigate how antifreeze peptides regulate cell physiological functions during the freezing process. METHODS: We investigated the cryoprotective effect of rsfAFP on the physiological functions of S. thermophilus under freezing stress by measuring cellular metabolism activity, intracellular enzyme activity, cell membrane characterization, and cell apoptosis. The mechanism by which rsfAFP impacts S. thermophilus physiological functions under freezing stress was investigated using multispectral techniques and cryo-TEM. RESULTS: We show that a recombinant antifreeze peptide (rsfAFP) interacts with the extracellular capsular polysaccharides and peptidoglycan of Streptococcus thermophilus and ice to cover the outer layer of the membrane, forming a dense protective layer that regulates the molecular structure of extracellular ice crystals, which results in reduced extracellular membrane damage, depressed apoptosis and increased intracellular metabolic activity. This interaction mechanism was indicated by the fact that S. thermophilus better maintained its permeability barrier, membrane fluidity, membrane structural integrity, and cytoplasmic membrane potential during freezing stress with rsfAFP treatment. CONCLUSION: These results provide new insights into the mechanism by which rsfAFP regulates frozen cellphysiological functionsand apoptosis under freezing stress.