X-Message-Number: 13066
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. 

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: 

Issue/Part/Supplement: 2
ISSN: 0011-2240

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