Structure and Substrate Binding Properties of cobB, a Sir2 Homolog Protein Deacetylase From Escherichia Coli

J Mol Biol. 2004 Mar 26;337(3):731-41. doi: 10.1016/j.jmb.2004.01.060.

Abstract

Sirtuins are NAD+-dependent protein deacetylase enzymes that are broadly conserved from bacteria to human, and have been implicated to play important roles in gene regulation, metabolism and longevity. cobB is a bacterial sirtuin that deacetylates acetyl-CoA synthetase (Acs) at an active site lysine to stimulate its enzymatic activity. Here, we report the structure of cobB bound to an acetyl-lysine containing non-cognate histone H4 substrate. A comparison with the previously reported archaeal and eukaryotic sirtuin structures reveals the greatest variability in a small zinc-binding domain implicated to play a particularly important role in substrate-specific binding by the sirtuin proteins. Comparison of the cobB/histone H4 complex with other sirtuin proteins in complex with acetyl-lysine containing substrates, further suggests that contacts to the acetyl-lysine side-chain and beta-sheet interactions with residues directly C-terminal to the acetyl-lysine represent conserved features of sirtuin-substrate recognition. Isothermal titration calorimetry studies were used to compare the affinity of cobB for a variety of cognate and non-cognate acetyl-lysine-bearing peptides revealing an exothermic reaction with relatively little discrimination between substrates. In contrast, similar studies employing intact acetylated Acs protein as a substrate reveal a binding reaction that is endothermic, suggesting that cobB recognition of substrate involves a burial of hydrophobic surface and/or structural rearrangement involving substrate regions distal to the acetyl-lysine-binding site. Together, these studies suggest that substrate-specific binding by sirtuin proteins involves contributions from the zinc-binding domain of the enzyme and substrate regions distal to the acetyl-lysine-binding site.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Escherichia coli Proteins / chemistry*
  • Histones
  • Lysine / chemistry
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Sequence Alignment
  • Sirtuins / chemistry*
  • Structural Homology, Protein
  • Substrate Specificity

Substances

  • Escherichia coli Proteins
  • Histones
  • Sirtuins
  • Lysine

Associated data

  • PDB/1S5P