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Models of the Protocellular Structures, Functions and EvolutionIn the absence of extinct or extant record of protocells, the most direct way to test our understanding of the origin of cellular life is to construct laboratory models that capture important features of protocellular systems. Such efforts are currently underway in a collaborative project between NASA-Ames, Harvard medical School and University of California. They are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures. The centerpiece of this project is a method for the in vitro evolution of protein enzymes toward arbitrary catalytic targets. A similar approach has already been developed for nucleic acids: First, a very large population of candidate molecules is generated using a random synthetic approach. Next, the small numbers of molecules that can accomplish the desired task are selected. These molecules are next vastly multiplied using the polymerase chain reaction. A mutagenic approach, in which the sequences of selected molecules are randomly altered, can yield further improvements in performance or alterations of specificities. Unfortunately, the catalytic potential of nucleic acids is rather limited. Proteins are more catalytically capable but cannot be directly amplified. In the new technique, this problem is circumvented by covalently linking each protein of the initial, diverse, pool to the RNA sequence that codes for it. Then, selection is performed on the proteins, but the nucleic acids are replicated. To date, we have obtained "a proof of concept" by evolving simple, novel proteins capable of selectively binding adenosine tri-phosphate (ATP). Our next goal is to create an enzyme that can phosphorylate amino acids and another to catalyze the formation of peptide bonds in the absence of nucleic acid templates. This latter reaction does not take place in contemporary cells. once developed, these enzymes will be encapsulated in liposomes so that they will function in a simulated cellular environment. To provide a continuous energy supply, usually needed to activate the substrates, an energy transduction complex which generates ATP from adenosine diphosphate, inorganic phosphate and light will be used. This system, consisting of two modern proteins, ATP synthase and bacteriorhodopsin, has already been built and shown to work efficiently. By coupling chemical synthesis to such a system, it will be possible to drive chemical reactions by light if only the substrates for these reactions are supplied.
Document ID
20010067374
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Pohorille, Andrew
(NASA Ames Research Center Moffett Field, CA United States)
New, Michael
(NASA Ames Research Center Moffett Field, CA United States)
Keefe, Anthony
(Massachusetts General Hospital Boston, MA United States)
Szostak, Jack W.
(Massachusetts General Hospital Boston, MA United States)
Lanyi, Janos F.
(California Univ. Irvine, CA United States)
DeVincenzi, Donald L.
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Subject Category
Life Sciences (General)
Meeting Information
Meeting: Frontiers of Life
Location: Blois
Country: France
Start Date: June 25, 2000
End Date: July 1, 2000
Funding Number(s)
PROJECT: RTOP 344-38-22-06
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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