CRYSTAL STRUCTURE OF CTP-LIGATED T STATE ASPARTATE TRANSCARBAMOYLASE AT 2.5 ANGSTROMS RESOLUTION: IMPLICATIONS FOR ATCASE MUTANTS AND THE MECHANISM OF NEGATIVE COOPERATIVITY

ASN B 132 - ASP B 133 OMEGA =147.63 PEPTIDE BOND DEVIATES SIGNIFICANTLY FROM TRANS CONFORMATION

Crystal structure of CTP-ligated T state aspartate transcarbamoylase at 2.5 A resolution: implications for ATCase mutants and the mechanism of negative cooperativity.

Structural Consequences of Effector Binding to the T State of Aspartate Carbamoyltransferase: Crystal Structures of the Unligated and ATP-and Ctp-Complexed Enzymes at 2.6 Angstroms Resolution

Structural Asymmetry in the Ctp-Liganded Form of Aspartate Carbamoyltransferase from Escherichia Coli

Location of Amino Acid Alterations in Mutants of Aspartate Transcarbamoylase: Structural Aspects of Interallelic Complementation

Nucleotide Sequence of the Structural Gene (Pyrb) that Encodes the Catalytic Polypeptide of Aspartate Transcarbamoylase of Escherichia Coli

Amino Acid Sequence of the Catalytic Subunit of Aspartate Transcarbamoylase from Escherichia Coli

Aspartate carbamoyltransferase catalytic chain

Aspartate carbamoyltransferase regulatory chain

ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELLKHKVIASCFFEASTRTRLSFETSMHRLGASVVGFSDSANTS
LGKKGETLADTISVISTYVDAIVMRHPQEGAARLATEFSGNVPVLNAGDGSNQHPTQTLLDLFTIQETQGRLDNLHVAMV
GDLKYGRTVHSLTQALAKFDGNRFYFIAPDALAMPQYILDMLDEKGIAWSLHSSIEEVMAEVDILYMTRVQKERLDPSEY
ANVKAQFVLRASDLHNAKANMKVLHPLPRVDEIATDVDKTPHAWYFQQAGNGIFARQALLALVLNRDLVL

MTHDNKLQVEAIKRGTVIDHIPAQIGFKLLSLFKLTETDQRITIGLNLPSGEMGRKDLIKIENTFLSEDQVDQLALYAPQ
ATVNRIDNYEVVGKSRPSLPERIDNVLVCPNSNCISHAEPVSSSFAVRKRANDIALKCKYCEKEFSHNVVLAN

THE AMINO ACID SEQUENCE OF ESCHERICHIA COLI ATCASE USED IN
THIS ENTRY REPRESENTS A DEPARTURE FROM THE SEQUENCE USED IN
PREVIOUS ATCASE STRUCTURES FROM THE SAME LABORATORY. THE
NEW AMINO ACID ASSIGNMENTS FOR FIVE OF THE RESIDUES IN EACH
CATALYTIC-REGULATORY SUBUNIT ARE NOW IN ACCORD WITH THE
DNA-DETERMINED AMINO ACID SEQUENCE MOST RECENTLY DEFINED
FOR THIS ENZYME. THE CHANGES ARE AS FOLLOWS:

PREVIOUS PRESENT
GLN A 60 GLU A 60
GLN A 147 GLU A 147
GLU A 149 GLN A 149
GLU A 196 GLN A 196
GLY B 8 GLN B 8
GLN C 60 GLU C 60
GLN C 147 GLU C 147
GLU C 149 GLN C 149
GLU C 196 GLN C 196
GLY D 8 GLN D 8

GLN 8 IS THE ONLY RESIDUE WHICH INVOLVED MORE THAN A SINGLE
ATOM CHANGE AND, AS A RESULT, IT IS THE ONLY RESIDUE IN
THIS LIST WHICH REQUIRED A REEXAMINATION OF THE
CRYSTALLOGRAPHIC DATA IN ADDITION TO THE REEXAMINATION OF
THE CHEMICAL ENVIRONMENT THAT WAS PERFORMED FOR ALL OF
THESE RESIDUES. OMIT MAPS BASED ON THE CTP-LIGATED ENZYME
DATA (SEE PAPER CITED ON *JRNL* RECORDS ABOVE) WERE
CREATED, AND IN BOTH RESIDUES WITHIN THE ASYMMETRIC UNIT
(GLN B 8 AND GLN D 8) ELECTRON DENSITY CONSISTENT WITH THE
GLUTAMINE SIDE CHAINS WAS IDENTIFIED, ALTHOUGH IT WAS NOT
POSSIBLE TO POSITION THE SIDE CHAINS WITH CERTAINTY IN THIS
ELECTRON DENSITY. CONSEQUENTLY, GLN 8 IS IDENTIFIED
PROPERLY AS A GLUTAMINE BUT IT LACKS THE SIDE CHAIN ATOMS.
THERE IS STILL AN UNRESOLVED CONFLICT IN THE LITERATURE
REGARDING THE IDENTITY OF RESIDUE 220 OF THE CATALYTIC
CHAIN (SEE THE PAPERS CITED AS REFERENCES 3 - 5 ABOVE).
SINCE THERE WAS NO UNEQUIVOCAL CRYSTALLOGRAPHIC EVIDENCE
FOR A VALINE AT THIS POSITION (REFERENCES 4 AND 5), ALA
(REFERENCE 3) WAS LEFT IN THIS SITE.