1H44

R210L N-TERMINAL LOBE HUMAN LACTOFERRIN

Summary for 1H44

• Entry DOI: 10.2210/pdb1h44/pdb
• Related: 1B0L 1BKA 1CB6 1DSN 1EH3 1FCK 1H43 1H45 1HSE 1L5T 1LCF 1LCT 1LFG 1LFH 1LFI 1LGB 1VFD 1VFE
• Descriptor: LACTOFERRIN, FE (III) ION, CARBONATE ION, ... (4 entities in total)
• Functional Keywords: metal transport, iron transport, metal binding
• Biological source: HOMO SAPIENS (HUMAN)
• Cellular location: Secreted: P02788
• Total number of polymer chains: 1
• Total formula weight: 37222.03

Authors

Peterson, N.A.,Arcus, V.L.,Anderson, B.F.,Jameson, G.B.,Tweedie, J.W.,Baker, E.N. (deposition date: 2002-10-03, release date: 2002-11-28, Last modification date: 2024-11-20)

Primary citation

Peterson, N.A.,Arcus, V.L.,Anderson, B.F.,Tweedie, J.W.,Jameson, G.B.,Baker, E.N.
"Dilysine Trigger" in Transferrins Probed by Mutagenesis of Lactoferrin: Crystal Structures of the R210G, R210E, and R210L Mutants of Human Lactoferrin
Biochemistry, 41:14167-, 2002

PubMed Abstract: The mammalian iron-binding proteins lactoferrin (Lf) and transferrin (Tf) bind iron very tightly, but reversibly. Despite homologous structures and essentially identical iron binding sites, Tf begins to release iron at pH 6.0, whereas Lf retains iron to pH approximately 3.5. This difference in iron retention gives the two proteins different biological roles. Two lysine residues, Lys 206 and Lys 296, which form a hydrogen-bonded dilysine pair in human Tf, have been shown to strongly influence iron release from the N-lobe. The equivalent residues in human Lf are Arg 210 and Lys 301, and we have here mutated Arg 210 in the N-lobe half-molecule of human lactoferrin, Lf(N), to probe its role in iron release. The Lf(N) mutants R210G, R210E, and R210L were expressed, purified, and crystallized, and their crystal structures were determined and refined at resolutions of 1.95 A (R210G), 2.2 A (R210E), and 2.0 A (R210L). The overall structures are very similar to that of wild-type Lf(N), but with small differences in domain orientations. In each of the mutants, however, Lys 301 (equivalent to Lys 296 in Tf) changes its conformation to fill the space occupied by Arg 210 Neta2 in wild-type Lf(N), interacting with the two tyrosine ligands Tyr 92 and Tyr 192. By comparison with other Lf and Tf structures, we conclude that Lys 301 (or Lys 296 in Tf) only occupies this site when residue 210 (206 in Tf) is nonpositive (neutral as in R210G and R210L or negative as in R210E). Thus, Lys 206 in the Tf dilysine pair is identified as having a depressed pK(a). Three specific sites are variably occupied by polar groups in the Lf mutants and other Lf and Tf proteins, and when coupled with iron-release data, these give new insights into the factors that most influence iron retention at low pH.

PubMed: 12450380
DOI: 10.1021/BI020443A

Experimental method

X-RAY DIFFRACTION (2 Å)