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(NAS Colloquium) Proteolytic Processing and Physiological Regulation (1999) / Chapter Skim
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The catalytic sites of 20S proteasomes and their role in subunit maturation: A mutational and crystallographic study
Pages 10976-10983

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
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From page 10976...
... Based on the crystal structure of the T acidophilum 20S proteasome, the distance between active site threonines was suggested as the molecular ruler that determines the length distribution of proteasome generated peptides (9~.
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From page 10977...
... These data substantiate previous biochemical findings on ,B7 maturation in the ,B2T1A single and 131TlA 132TlA double mutant, which led to the hypothesis that inactive ,B-subunits are processed by the closest active neighbor subunit (11~. The intermediately processed propeptides of 136 and ,B7 had been found in well defined locations in the molecular structure of the wild-type protein such that their N termini lie at the inner annulus of the ,8-subunit rings far removed from the sites of proteolytic cleavage defined here (7~.
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From page 10978...
... ing and fixation at the final sites seen in the crystal structure. In 131TlA 132TlA, the full length propeptide of I31 and the intermediately processed propeptides of {32, ,86, and ,B7 have well defined electron density up to residues Met-19 (91)
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From page 10979...
... In ,B6, the cut occurs between Ala-17 and Ser-16, as analyzed by Edman degradation of an HPLC fraction. In the ,BlTlA 132TlA double mutant, a component with cleavage between Thr-14 and Pro-13 is found by mass spectrometry.
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From page 10980...
... The conservative exchange of Lys33 to arginine abolishes both autolysis and proteolysis in T acidophilum proteasomes (25~.
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From page 10981...
... The activity against chromogenic substrates of a particular subunit is insignificantly altered by the presence or absence of intact sites of other subunits. We had previously shown that the covalent binding of a specific bound irreversible inhibitor of ,B2 has no significant influence on the PGPH and chymotryptic activity associated with ,B1 and ,135 and does not show noticeable structural changes (26~.
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From page 10982...
... The crystal structure analysis at 1.95-A resolution shows defined electron density at I36 for all nine residues of the partially processed propeptide, but it is substantially lower than in the wild type and particularly blurred at residues Asn-2 and Gly-1. Temperature factors of the propeptide are very high.
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From page 10983...
... While this paper was in press, a publication by Arendt and Hochstrasser (28) appeared suggesting acetylation of ,B1, ,B2, and ,B5 subunits by genetic methods in mutants lacking the respective propeptides.
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Key Terms

  • wild type
  • mass spectrometry
  • double mutant
  • active site
  • intermediately processed

  • electron density
  • crystal structure
  • opposite ring
  • inactive subunits
  • amino acid

  • proteasome mutants
  • processed propeptides
  • mutant proteasomes
  • active sites
  • defined electron

  • chymotryptic activity
  • additionally observed
  • proteasome maturation
  • structural analysis
  • sequence analysis

  • acid preferring
  • inner annulus
  • cleavage sites
  • final forms
  • edman degradation

  • acidophilum proteasomes
  • molecular weight
  • quintuple mutant
  • double mutants
  • site threonines


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