Ti(IV) bound human serum transferrin

Experimental Data Snapshot

  • Resolution: 2.68 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.204 

wwPDB Validation   3D Report Full Report

This is version 1.5 of the entry. See complete history


Unusual Synergism of Transferrin and Citrate in the Regulation of Ti(IV) Speciation, Transport, and Toxicity.

Tinoco, A.D.Saxena, M.Sharma, S.Noinaj, N.Delgado, Y.Quinones Gonzalez, E.P.Conklin, S.E.Zambrana, N.Loza-Rosas, S.A.Parks, T.B.

(2016) J Am Chem Soc 138: 5659-5665

  • DOI: https://doi.org/10.1021/jacs.6b01966
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Human serum transferrin (sTf) is a protein that mediates the transport of iron from blood to cells. Assisted by the synergistic anion carbonate, sTf transports Fe(III) by binding the metal ion in a closed conformation. Previous studies suggest sTf's role as a potential transporter of other metals such as titanium. Ti is a widely used metal in colorants, foods, and implants. A substantial amount of Ti is leached into blood from these implants. However, the fate of the leached Ti and its transport into the cells is not known. Understanding Ti interaction with sTf assumes a greater significance with our ever increasing exposure to Ti in the form of implants. On the basis of in vitro studies, it was speculated that transferrin can bind Ti(IV) assisted by a synergistic anion. However, the role and identity of the synergistic anion(s) and the conformational state in which sTf binds Ti(IV) are not known. Here we have solved the first X-ray crystal structure of a Ti(IV)-bound sTf. We find that sTf binds Ti(IV) in an open conformation with both carbonate and citrate as synergistic anions at the metal binding sites, an unprecedented role for citrate. Studies with cell lines suggest that Ti(IV)-sTf is transported into cells and that sTf and citrate regulate the metal's blood speciation and attenuate its cytotoxic property. Our results provide the first glimpse into the citrate-transferrin synergism in the regulation of Ti(IV) bioactivity and offers insight into the future design of Ti(IV)-based anticancer drugs.

  • Organizational Affiliation

    Department of Biological Sciences, Purdue University , 240 S. Martin Jischke Drive, Hockmeyer Hall, West Lafayette, Indiana 47907, United States.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
698Homo sapiensMutation(s): 0 
Gene Names: TFPRO1400
UniProt & NIH Common Fund Data Resources
Find proteins for P02787 (Homo sapiens)
Explore P02787 
Go to UniProtKB:  P02787
PHAROS:  P02787
GTEx:  ENSG00000091513 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP02787
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CIT

Download Ideal Coordinates CCD File 
C [auth A]
D [auth A]
E [auth A]
F [auth A]
G [auth A]
C [auth A],
D [auth A],
E [auth A],
F [auth A],
G [auth A],
H [auth A],
K [auth B],
L [auth B],
M [auth B],
N [auth B],
O [auth B]
C6 H8 O7
Query on CO3

Download Ideal Coordinates CCD File 
J [auth A],
Q [auth B]
C O3
Query on 4TI

Download Ideal Coordinates CCD File 
I [auth A],
P [auth B]
Experimental Data & Validation

Experimental Data

  • Resolution: 2.68 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.202 
  • R-Value Observed: 0.204 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 88.275α = 90
b = 102.016β = 90
c = 197.899γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
HKL-2000data scaling
PDB_EXTRACTdata extraction
HKL-2000data reduction

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Institutes of Health/National Cancer Institute (NIH/NCI)United States1SC1CA190504-01
The Puerto Rico Science, Technology, and Research TrustPuerto Rico2013-000019
University of Puerto Rico Score Stabilization GrantPuerto Rico--

Revision History  (Full details and data files)

  • Version 1.0: 2016-04-27
    Type: Initial release
  • Version 1.1: 2016-05-11
    Changes: Database references
  • Version 1.2: 2016-05-18
    Changes: Database references
  • Version 1.3: 2017-09-20
    Changes: Author supporting evidence, Derived calculations
  • Version 1.4: 2019-12-04
    Changes: Author supporting evidence
  • Version 1.5: 2023-09-27
    Changes: Data collection, Database references, Refinement description