Structural transitions in crystals of native aspartate carbamoyltransferase.

J. E. Gouaux, W. N. Lipscomb

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17 Scopus citations


Screened precession x-ray photographs of crystals of native aspartate carbamoyltransferase (EC, from Escherichia coli) ligated with L-aspartate and phosphate reveal the presence of a crystal unit-cell dimension that is intermediate between the T (tense) and R (relaxed) states. Characterizing the intermediate (I) crystal is a c-axis unit-cell dimension of 149 A, halfway between the c-axis length of the T (c = 142 A) and R (c = 156 A) states, in the space group P321. Preservation of the P321 space group indicates that the intermediate crystal form retains a threefold axis of symmetry, and therefore the enzyme has at minimum a threefold axis; however, we do not know whether the molecular twofold axis is conserved. The I crystals are formed by soaking T-state crystals with L-aspartate and phosphate. By raising the concentration of L-aspartate we can further transform the I crystals, without fragmentation, to a form that has the same unit-cell dimensions as R-state crystals grown in the presence of N-(phosphonoacetyl)-L-aspartate.

Original languageEnglish (US)
Pages (from-to)845-848
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
StatePublished - Feb 1989
Externally publishedYes

ASJC Scopus subject areas

  • General


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