Making Proteins Takes a Ribozyme

From: andrew mandell (
Date: Fri Aug 18 2000 - 10:58:16 EDT

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    Hey list.
    Just thought this was interesting but I couldn't access the implications
    for evolution page.
    from this week in science mailer
    It would seem that proteins make the world of the cell go around. They
    regulate the intake of nutrients, some of which are combusted to produce
    energy; other nutrients are used as building blocks to make genetic
    components such as DNA and RNA or to make structural and storage materials
    such as lipids and carbohydrates. All of these processes are catalyzed by
    proteins. Now we learn that proteins themselves are made in the ribosome, a
    large complex of proteins and RNA, by reactions catalyzed by ribosomal RNA
    (rRNA). The high-resolution structure of the large subunit of the ribosome
    is described by Ban et al. (p. 905). This subunit, made of approximately
    3000 ribonucleotides and 30 distinct proteins, catalyzes the synthesis of
    the peptide bond, which is the linkage that joins amino acids in proteins.
    The active site for this reaction is entirely surrounded by rRNA; the main
    role of the protein components appears to be that of lending structural
    stability. The structure of the subunit complexed with substrate analogs,
    described by Nissen et al. (p. 920; see the cover), confirms that the
    substrate binding-site interactions are mediated by rRNA. A universally
    conserved adenine base is positioned to act as a general acid-base catalyst
    for the synthesis reaction. The role of this adenine is further
    characterized by Muth et al. (p. 947). It displays a substantial shift in
    its acidity constant as a result of its near-neighbor interactions within
    the active site (a catalytic resource thought previously to be possessed
    only by proteins). The biochemical aspects of the proposed mechanism (which
    appears indistinguishable from that of serine proteases, except that it
    acts in reverse) and evolutionary implications are discussed in a
    Perspective by Cech.

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