4V2Q: Ironing Out Their Differences: Dissecting The Structural Determinants Of A Phenylalanine Aminomutase And Ammonia Lyase

Deciphering the structural features that functionally separate ammonia lyases from aminomutases is of interest because it may allow for the engineering of more efficient aminomutases for the synthesis of unnatural amino acids (e.g., beta-amino acids). However, this has proved to be a major challenge that involves understanding the factors that influence their activity and regioselectivity differences. Herein, we report evidence of a structural determinant that dictates the activity differences between a phenylalanine ammonia lyase (PAL) and aminomutase (PAM). An inner loop region that closes the active sites of both PAM and PAL was mutated within PAM (PAM residues 77-97) in a stepwise approach to study the effects when the equivalent residue(s) found in the PAL loop were introduced into the PAM loop. Almost all of the single loop mutations triggered a lyase phenotype in PAM. Experimental and computational evidence suggest that the induced lyase features result from inner loop mobility enhancements, which are possibly caused by a 310-helix cluster, flanking alpha-helices, and hydrophobic interactions. These findings pinpoint the inner loop as a structural determinant of the lyase and mutase activities of PAM.
PDB ID: 4V2QDownload
MMDB ID: 125511
PDB Deposition Date: 2014/10/14
Updated in MMDB: 2014/12
Experimental Method:
x-ray diffraction
Resolution: 1.95  Å
Source Organism:
Similar Structures:
Biological Unit for 4V2Q: tetrameric; determined by author and by software (PISA)
Molecular Components in 4V2Q
Label Count Molecule
Proteins (4 molecules)
Phenylalanine Ammonia-lyase
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB