X-Message-Number: 13066 From: Date: Thu, 6 Jan 2000 10:39:35 EST Subject: protein antifreezes Re John Clark's suggestion about using bacteria to grow protein antifreezes: 1. Isn't it necessary to get the antifreeze protein inside the organelles of cells to prevent crystals inside? So the protein would have to be engineered to be taken in by many different types of cells, then also engineered to be targeted to the various organelles inside (for example, adding an SKL sequence targets proteins to the peroxisomes.) If this isn't true, i.e. if the proteins were only necessary outside the cells, the proteins would still have to be separated from the bacteria and protected from our immune system. This could be done by simply knocking out the immune system with immunosuppressive drugs (or more intelligently, just selectively killing the T Cells which respond to the antifreeze protein) and then injecting the purified protein. I suspect that the proteins are necessary inside cells and organelles; see the Medline abstract below which suggests that injection of antifreeze proteins extracellularly actually causes more cell death. I would appreciate e-mails on this if I'm wrong. 2. I would mention also that bacteria are not suitable for producing all proteins. Many proteins have to be processed by 1. cleavage of amino acid sequences in the endoplasmic reticulum, and 2. the addition of sugars in the Golgi apparatus. Bacteria don't have ER or Golgi apparatus, so often proteins sequenced and then expressed in bacteria don't fold into the right shape. This is why yeast are often used now for protein production. --Bill Walker ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ ----------------------- An in vivo study of antifreeze protein adjuvant cryosurgery. ------------------------------------------------------------------------------ -- Abstract: Cryosurgery employs freezing to destroy undesirable tissue. However, under certain thermal conditions, frozen tissues survive. The survival of frozen undesirable tissue may lead to complications, such as recurrence of cancer. In a study of nude mice with subcutaneous metastatic prostate tumors, we showed that the preoperative injection of a phosphate-buffered saline solution with 10 mg/ml antifreeze protein of type I into the tumor prior to freezing enhances destruction under thermal conditions which normally yield cell survival. This suggests that the adjunctive use of antifreeze proteins in cryosurgery may reduce the complications from undesirable tissues that survive freezing. Author: Pham L Dahiya R Rubinsky B Address: Bioengineering Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA. Abbreviated Journal Title: Cryobiology Journal Title Code: DT3 Date Of Publication: 1999 Mar Journal Volume: 38 Page Numbers: 169 through 175 Country of Publication: UNITED STATES Language of Article: Eng Type Of Article: JOURNAL ARTICLE Issue/Part/Supplement: 2 ISSN: 0011-2240 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13066