1SSB

A STRUCTURAL INVESTIGATION OF CATALYTICALLY MODIFIED F12OL AND F12OY SEMISYNTHETIC RIBONUCLEASES

Summary for 1SSB

• Entry DOI: 10.2210/pdb1ssb/pdb
• Descriptor: RIBONUCLEASE A, SULFATE ION, ... (4 entities in total)
• Functional Keywords: hydrolase(endoribonuclease)
• Biological source: Bos taurus (bovine)
• Total number of polymer chains: 2
• Total formula weight: 14667.31

Authors

Demel, V.S.J.,Doscher, M.S.,Glinn, M.A.,Martin, P.D.,Ram, M.L.,Edwards, B.F.P. (deposition date: 1993-08-03, release date: 1994-09-30, Last modification date: 2024-11-06)

Primary citation

deMel, V.S.,Doscher, M.S.,Glinn, M.A.,Martin, P.D.,Ram, M.L.,Edwards, B.F.
Structural investigation of catalytically modified F120L and F120Y semisynthetic ribonucleases.
Protein Sci., 3:39-50, 1994

PubMed Abstract: The structures of two catalytically modified semisynthetic RNases obtained by replacing phenylalanine 120 with leucine and tyrosine have been determined and refined at a resolution of 2.0 A (R = 0.161 and 0.184, respectively). These structures have been compared with the refined 1.8-A structure (R = 0.204) of the fully active phenylalanine-containing enzyme (Martin PD, Doscher MS, Edwards BFP, 1987, J Biol Chem 262:15930-15938) and with the catalytically defective D121A (2.0 A, R = 0.172) and D121N (2.0 A, R = 0.186) analogs (deMel VSJ, Martin PD, Doscher MS, Edwards BFP, 1992, J Biol Chem 267:247-256). The movement away from the active site of the loop containing residues 65-72 is seen in all three catalytically defective analogs--F120L, D121A, and D121N--but not in the fully active (or hyperactive) F120Y. The insertion of the phenolic hydroxyl of Tyr 120 into a hydrogen-bonding network involving the hydroxyl group of Ser 123 and a water molecule in F120Y is the likely basis for the hyperactivity toward uridine 2',3'-cyclic phosphate previously found for this analog (Hodges RS, Merrifield RB, 1974, Int J Pept Protein Res 6:397-405) as well as the threefold increase in KM for cytidine 2',3'-cyclic phosphate found for this analog by ourselves.

PubMed: 8142897

Experimental method

X-RAY DIFFRACTION (2 Å)