1QJM

Crystal Structure of a Complex of Lactoferrin with a Lanthanide Ion (SM3+) at 3.4 Angstrom Resolution

Summary for 1QJM

• Entry DOI: 10.2210/pdb1qjm/pdb
• Descriptor: LACTOFERRIN, SAMARIUM (III) ION, CARBONATE ION (3 entities in total)
• Functional Keywords: lactoferrin, complex, iron binding, transferrin
• Biological source: EQUUS CABALLUS (HORSE)
• Total number of polymer chains: 1
• Total formula weight: 75791.94

Authors

Sharma, A.K.,Singh, T.P. (deposition date: 1999-06-27, release date: 1999-08-26, Last modification date: 2023-12-13)

Primary citation

Sharma, A.K.,Singh, T.P.
Lactoferrin-Metal Interactions: First Crystal Structure of a Complex of Lactoferrin with a Lanthanide Ion (Sm3+) at 3.4 Angstrom Resolution
Acta Crystallogr.,Sect.D, 55:1799-, 1999

PubMed Abstract: Lactoferrin is an important member of the transferrin family. A characteristic property of transferrins is their ability to bind very tightly (K(app) approximately/= 10(20)) but reversibly two Fe(3+) ions. The structural consequences of binding a metal other than Fe(3+) have been examined by crystallographic analysis at 3.4 A resolution of mare samarium-lactoferrin (Sm(2)Lf). The structure was refined to an R factor of 0.219 for 8776 reflections in the resolution range 17.0-3.4 A. The samarium geometry (distorted octahedral coordination) is similar in both lobes. However, the anion interactions are quite different in the two lobes. In the N lobe, the anion is able to form only two hydrogen bonds instead of the four observed in the C lobe of Sm(2)Lf and the six observed in Fe(2)Lf. This is because Arg121, Thr117 and Gly124 have moved away from the anion as a consequence of the binding of the Sm(3+) ion. The protein ligands in the binding cleft of Sm(2)Lf show large displacements, but the overall protein structure remains the same. The binding of Sm(3+) by lactoferrin shows that the protein is capable of sequestering ions of different sizes and charges, though with reduced affinity. This conclusion should be true of other transferrins also.

PubMed: 10531475
DOI: 10.1107/S0907444999009865

Experimental method

X-RAY DIFFRACTION (3.4 Å)