PDBsum entry 1ht3

Hydrolase

PDB id: 1ht3

Contents

Protein chain

279 a.a. *

Metals

_CA

_HG ×2

Waters ×244

* Residue conservation analysis

PDB id:

1ht3

Name:

Hydrolase

Title:

Mercury induced modifications in the stereochemistry of the active site through cys-73 in a serine protease: crystal structure of the complex of a partially modified proteinase k with mercury at 1.8 a resolution

Structure:

Proteinase k. Chain: a. Ec: 3.4.21.64

Source:

Engyodontium album. Organism_taxid: 37998

Resolution:

1.80Å R-factor: 0.164 R-free: 0.221

Authors:

S.Gourinath

Key ref:

S.Gourinath et al. (2001). Mercury induced modifications in the stereochemistry of the active site through Cys-73 in a serine protease--crystal structure of the complex of a partially modified proteinase K with mercury at 1.8 A resolution. Indian J Biochem Biophys, 38, 298-302. PubMed id: 11886076

Date:

27-Dec-00 Release date: 27-Jun-01

Protein chain

P06873  (PRTK_PARAQ) -  Proteinase K from Parengyodontium album

Seq: 384 a.a.

Struc: 279 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.3.4.21.64 - peptidase K.
• Reaction: Hydrolysis of keratin and of other proteins, with subtilisin-like specificity. Hydrolyzes peptides amides.

Indian J Biochem Biophys 38:298-302 (2001)

PubMed id: 11886076

Mercury induced modifications in the stereochemistry of the active site through Cys-73 in a serine protease--crystal structure of the complex of a partially modified proteinase K with mercury at 1.8 A resolution.

S.Gourinath, M.Degenhardt, S.Eschenburg, K.Moore, L.J.Delucas, C.Betzel, T.P.Singh.

ABSTRACT

Proteinese K (PK) isolated from Tritirachium album Limber was crystallized with HgCl2 in excess, under microgravity conditions. The intensity data were collected at 4 degrees C to 1.8 A resolution and the final R-factor after refinement for all the reflections was 0.164. Mercury has been found at two sites with partial occupancies (0.4 and 0.6) which are at distances of 2.48 A and 2.58 A respectively from Cys-73 Sgamma. The Cys-73 in the enzyme structure is located close to the active site residue, His-69. This region is completely buried and is not accessible to the solvent. It is rather tightly packed. Therefore, the binding of mercury distorts the stereochemistry of the neighbouring residues including those belonging to the catalytic triad. As a result of this, the Ogamma of Ser-224 is displaced by 0.6 A which causes the inactivation of proteinase K by increasing the H-bond distance to 3.7 A between Ser-224 Ogamma and His-69 Nepsilon2.