1keh

Precursor structure of cephalosporin acylase

Overview

Autocatalytic proteolytic cleavage is a frequently observed, post-translational modification in proteins. Cephalosporin acylase (CA) is, a recently identified member of the N-terminal hydrolase family that is, activated from an inactive precursor by autoproteolytic processing, generating a new N-terminal residue, which is either a Ser or a Thr. The, N-terminal Ser or Thr becomes a nucleophilic catalytic center for, intramolecular and intermolecular amide cleavages. The gene structure of, the open reading frame of CAs generally consists of a signal peptide, followed by the alpha-subunit, a spacer sequence, and the beta-subunit, which are all translated into a single polypeptide chain, the CA, precursor. The precursor is post-translationally modified into an active, heterodimeric enzyme with alpha- and beta-subunits, first by, intramolecular cleavage and second by intermolecular cleavage. We solved, the first CA precursor structure (code 1KEH) from a class I CA from, Pseudomonas diminuta at a 2.5-A resolution that provides insight into the, mechanism of intramolecular cleavage. A conserved water molecule, stabilized by four hydrogen bonds in unusual pseudotetrahedral geometry, plays a key role to assist the OG atom of Ser(1beta) to generate a strong, nucleophile. In addition, the site of the secondary intermolecular, cleavage of CA is proposed to be the carbonyl carbon of Gly(158alpha), (Kim, S., and Kim, Y., (2001) J. Biol. Chem., 276, 48376-48381), which is, different from the situation in two other class I CAs.

About this Structure

1KEH is a Single protein structure of sequence from Brevundimonas diminuta. Full crystallographic information is available from OCA.

Reference

Precursor structure of cephalosporin acylase. Insights into autoproteolytic activation in a new N-terminal hydrolase family., Kim Y, Kim S, Earnest TN, Hol WG, J Biol Chem. 2002 Jan 25;277(4):2823-9. Epub 2001 Nov 8. PMID:11706000

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