Please note these web pages were prepared for a protein report assignment for a graduate course called Advanced Biochemistry and Molecular Biology BCMB8010 at the University of Georgia.  Questions about the report should be directed to Joseph Scott at: joscott@uga.edu.

 

Escherichia coli Hydrogenase Maturating Endopeptidase

 

Introduction (Abstract)

 

Escherichia coli has at least three operons that control the production of active hydrogenase enzyme under varying physiological conditions (1).  Each operon includes genes encoding a hydrogenase in addition to gene products involved in processing of the immature hydrogenase specific to that operon (2).  HycI is one of several enzymes involved in the maturation of E. coli hydrogenase 3 (1, 3, 4).  HycI acts as an endopeptidase to cleave exposed C-terminal residues of the hydrogenase large subunit.  The consensus sequence for cleavage in DPCXXCH(R) with cleavage occuring after a histidine or arginine residue (1).  Nickel, which has been shown to be part of the recognition site for the endopeptidase, is bound by the cysteine residues of the consensus sequence (4).  The endopeptidase itself does not contain any metal cofactors, however, crystallographic data suggest that during catalysis, the nickel of the large subunit is coordinated by three amino acid side chains (Glu16, Asp62, and His93) of the endopeptidase and and one water molecule (4).  A conformational change occurs after cleavage in which the consensus sequence bound nickel atom is brought to the interior of the large subunit and forms a metal center with an iron atom that is bound at the N-terminus of the large subunit.  This conformational change allows for the hydrogenase small subunit to complex with the large subunit resulting in a mature and active hydrogenase (4).

Most of the biochemical data available on endopeptidase activity during hydrogenase maturation was derived from HycI (1, 2, 4).  Unfortunately, HycI was unable to be crystallized.  However, HybD, an HycI homolog,  that processes E. coli hydrogenase 2 was able to be crystallized (4). Therefore, this enzyme report utilizes biochemical data from HycI studies and crystallographic data from HybD to discuss details relating the structural and functional aspects of the E. coli hydrogenase maturation endopeptidase.

 

References: 

  1. Rossmann, R., Maier, T., Lottspeich, F., and Bock, A (1995) Characterisation of from Escherichia coli involved in hydrogenase maturation  Eur. J. Biochem. 227, 545-550
  1. Paschos, A., Bauer, A., Zimmermann, A., Zehelein E., and Bock, A. (2002) HypF, a carbamoyl-phosphate converting enzyme involved in [NiFe] hydrogenase maturation J. Biol. Chem. 277, 49945-49951
  1. Theodoratou, E., Paschos, A., Magalon, A., Fritsche, E., Huber, R., and Bock, A. (2000) Nickel serves as a substrate recognition motif for the endopeptidase involved in hydrogenase maturation Eur. J. Biochem. 267, 1995-1999
  1. Fritsche, E., Paschos, A., Hans-Georg, B., Bock, A., and Huber, R. (1999) Crystal structure of the hydrogenase maturating endopeptidase HybD from Escherichia coli J. Mol. Biol. 989-998

 

Links:

PDF version of Enzyme Report

BCMB 8010 Class Database

Powerpoint Presentation