PDBsum entry 4zj2

Hydrolase

PDB id: 4zj2

Contents

Protein chain

265 a.a.

Waters ×214

PDB id:

4zj2

Name:

Hydrolase

Title:

Crystal structure of p-acrylamido-phenylalanine modified tem1 beta- lactamase from escherichia coli :e166n mutant

Structure:

Beta-lactamase tem. Chain: a. Synonym: irt-4,penicillinase,tem-1,tem-16/caz-7,tem-2,tem-24/caz-6, tem-3,tem-4,tem-5,tem-6,tem-8/caz-2. Engineered: yes. Mutation: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: bla, blat-3, blat-4, blat-5, blat-6. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.80Å R-factor: 0.168 R-free: 0.209

Authors:

H.Xiao,F.Nasertorabi,S.Choi,G.W.Han,S.A.Reed,C.S.Stevens,P.G.Schultz

Key ref:

H.Xiao et al. (2015). Exploring the potential impact of an expanded genetic code on protein function. Proc Natl Acad Sci U S A, 112, 6961-6966. PubMed id: 26038548 DOI: 10.1073/pnas.1507741112

Date:

28-Apr-15 Release date: 20-May-15

Protein chain

P62593  (BLAT_ECOLX) -  Beta-lactamase TEM from Escherichia coli

Seq: 286 a.a.

Struc: 265 a.a.*

* PDB and UniProt seqs differ at 4 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.5.2.6 - beta-lactamase.
• Pathway: Penicillin Biosynthesis and Metabolism
• Reaction: a beta-lactam + H2O = a substituted beta-amino acid
• Cofactor: Zn(2+)

DOI no: 10.1073/pnas.1507741112

Proc Natl Acad Sci U S A 112:6961-6966 (2015)

PubMed id: 26038548

Exploring the potential impact of an expanded genetic code on protein function.

H.Xiao, F.Nasertorabi, S.H.Choi, G.W.Han, S.A.Reed, R.C.Stevens, P.G.Schultz.

ABSTRACT

With few exceptions, all living organisms encode the same 20 canonical amino acids; however, it remains an open question whether organisms with additional amino acids beyond the common 20 might have an evolutionary advantage. Here, we begin to test that notion by making a large library of mutant enzymes in which 10 structurally distinct noncanonical amino acids were substituted at single sites randomly throughout TEM-1 β-lactamase. A screen for growth on the β-lactam antibiotic cephalexin afforded a unique p-acrylamido-phenylalanine (AcrF) mutation at Val-216 that leads to an increase in catalytic efficiency by increasing kcat, but not significantly affecting KM. To understand the structural basis for this enhanced activity, we solved the X-ray crystal structures of the ligand-free mutant enzyme and of the deacylation-defective wild-type and mutant cephalexin acyl-enzyme intermediates. These structures show that the Val-216-AcrF mutation leads to conformational changes in key active site residues-both in the free enzyme and upon formation of the acyl-enzyme intermediate-that lower the free energy of activation of the substrate transacylation reaction. The functional changes induced by this mutation could not be reproduced by substitution of any of the 20 canonical amino acids for Val-216, indicating that an expanded genetic code may offer novel solutions to proteins as they evolve new activities.