1HML

ALPHA_LACTALBUMIN POSSESSES A DISTINCT ZINC BINDING SITE

• PDB DOI: https://doi.org/10.2210/pdb1HML/pdb

• Classification: CALCIUM-BINDING PROTEIN
• Organism(s): Homo sapiens
• Mutation(s): No 


• Deposited: 1994-09-29 Released: 1995-01-26 
• Deposition Author(s): Ren, J., Stuart, D.I., Acharya, K.R.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.70 Å
• R-Value Work: 0.165 
• R-Value Observed: 0.165 

Literature

Alpha-lactalbumin possesses a distinct zinc binding site.

Ren, J., Stuart, D.I., Acharya, K.R.

(1993) J Biol Chem 268: 19292-19298

• PubMed: 8366079 
• Primary Citation of Related Structures:  
  1HML


• PubMed Abstract: 
  

  It has been proposed that the binding of Zn2+ to alpha-lactalbumin switches the conformation to one akin to a state intermediate in the folding of the protein. However, the high resolution x-ray crystal structure of human alpha-lactalbumin-Zn2+ complex at 1.7-A resolution (pH 7.6) does not reveal any significant change in conformation from the native state. The Zn2+ ion binds specifically in the "cleft" of alpha-lactalbumin (the region which forms the active site of the homologous protein lysozyme). This may suggest a possible role for Zn2+ binding in lactose synthase complex. The coordination of the Zn2+ ion involves a symmetry-related molecule in the crystal, the crystal contacts being stabilized by a SO4(2-) ion bound at the interface between three molecules.

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Organizational Affiliation: 

Oxford Centre for Molecular Sciences, New Chemistry Laboratory, United Kingdom.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 16.44 kDa 
• Atom Count: 1,102 
• Modelled Residue Count: 123 
• Deposited Residue Count: 142 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
ALPHA-LACTALBUMIN	A	142	Homo sapiens	Mutation(s): 0  EC: 2.4.1.22
UniProt & NIH Common Fund Data Resources
Find proteins for P00709 (Homo sapiens) Explore P00709  Go to UniProtKB:  P00709
PHAROS:  P00709 GTEx:  ENSG00000167531

Small Molecules

Ligands 3 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
SO4	D [auth A]	SULFATE ION O4 S QAOWNCQODCNURD-UHFFFAOYSA-L
ZN	C [auth A]	ZINC ION Zn PTFCDOFLOPIGGS-UHFFFAOYSA-N
CA	B [auth A]	CALCIUM ION Ca BHPQYMZQTOCNFJ-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.70 Å
• R-Value Work: 0.165 
• R-Value Observed: 0.165 
• Space Group: P 2₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 35.6	α = 90
b = 69.7	β = 90
c = 46.2	γ = 90

Software Package:

Software Name	Purpose
X-PLOR	model building
X-PLOR	refinement
X-PLOR	phasing

Structure Validation

Entry History 

Deposition Data

• Released Date: 1995-01-26 
Deposition Author(s): Ren, J., Stuart, D.I., Acharya, K.R.

Revision History  

• Version 1.0: 1995-01-26
  Type: Initial release
  
• Version 1.1: 2008-03-03
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 1.3: 2024-06-05
  Changes: Data collection, Database references, Derived calculations, Other
• Version 1.4: 2024-11-20
  Changes: Structure summary