Crystal structure of Human Senescence Marker Protein-30 (Zinc Bound)

Experimental Data Snapshot

  • Resolution: 1.92 Å
  • R-Value Free: 0.253 
  • R-Value Work: 0.224 
  • R-Value Observed: 0.225 

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Crystal structure of human senescence marker protein 30: insights linking structural, enzymatic, and physiological functions .

Chakraborti, S.Bahnson, B.J.

(2010) Biochemistry 49: 3436-3444

  • DOI: https://doi.org/10.1021/bi9022297
  • Primary Citation of Related Structures:  
    3G4E, 3G4H

  • PubMed Abstract: 

    Human senescence marker protein 30 (SMP30), which functions enzymatically as a lactonase, hydrolyzes various carbohydrate lactones. The penultimate step in vitamin-C biosynthesis is catalyzed by this enzyme in nonprimate mammals. It has also been implicated as an organophosphate hydrolase, with the ability to hydrolyze diisopropyl phosphofluoridate and other nerve agents. SMP30 was originally identified as an aging marker protein, whose expression decreased androgen independently in aging cells. SMP30 is also referred to as regucalcin and has been suggested to have functions in calcium homeostasis. The crystal structure of the human enzyme has been solved from X-ray diffraction data collected to a resolution of 1.4 A. The protein has a 6-bladed beta-propeller fold, and it contains a single metal ion. Crystal structures have been solved with the metal site bound with either a Ca(2+) or a Zn(2+) atom. The catalytic role of the metal ion has been confirmed by mutagenesis of the metal coordinating residues. Kinetic studies using the substrate gluconolactone showed a k(cat) preference of divalent cations in the order Zn(2+) > Mn(2+) > Ca(2+) > Mg(2+). Notably, the Ca(2+) had a significantly higher value of K(d) compared to those of the other metal ions tested (566, 82, 7, and 0.6 mum for Ca(2+), Mg(2+), Zn(2+), and Mn(2+), respectively), suggesting that the Ca(2+)-bound form may be physiologically relevant for stressed cells with an elevated free calcium level.

  • Organizational Affiliation

    Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
RegucalcinA [auth B],
B [auth A]
297Homo sapiensMutation(s): 0 
Gene Names: RGNSMP30
UniProt & NIH Common Fund Data Resources
Find proteins for Q15493 (Homo sapiens)
Explore Q15493 
Go to UniProtKB:  Q15493
GTEx:  ENSG00000130988 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ15493
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.92 Å
  • R-Value Free: 0.253 
  • R-Value Work: 0.224 
  • R-Value Observed: 0.225 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 64.365α = 90
b = 52.019β = 100.11
c = 85.832γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
PDB_EXTRACTdata extraction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2010-02-02
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-09-06
    Changes: Data collection, Database references, Derived calculations, Refinement description