1bjr
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COMPLEX FORMED BETWEEN PROTEOLYTICALLY GENERATED LACTOFERRIN FRAGMENT AND PROTEINASE K
OverviewOverview
Lactoferrin is an iron binding glycoprotein with a molecular weight of 80, kDa. The molecule is divided into two lobes representing the N-terminal, and C-terminal halves of the polypeptide chain, each containing an iron, binding site. The serine proteinases such as trypsin, chymotrypsin, and, pepsin hydrolyze lactoferrin into two unequal halves while proteinase K, divides this protein into two equal halves. In the first step of, hydrolysis by proteinase K, the C- and N-lobes, each having a molecular, weight of approximately 40 kDa, are generated. In the next step, the lobes, are further hydrolyzed into small molecular weight peptides. The, proteinase K isolated from the hydrolyzed product does not show enzymatic, activity suggesting that the enzyme is inhibited. Furthermore, the, hydrolysis experiments on N-lobe and C-lobe showed that the inhibitory, fragment came from the C-lobe. The purified lactoferrin fragment was found, to be a decapeptide with an amino acid sequence of, H2N-Val-Ala-Gln-Gly-Ala-Ala-Gly-Leu-Ala-COOH. The complex formed between, proteinase K and lactoferrin fragment was crystallized by microdialysis., The crystals belonged to the monoclinic space group P2(1) with cell, dimensions a = 44.4 A, b = 38.6 A, c = 79.2 A, beta = 105.8 degrees and Z, = 2. The crystal structure has been determined at 2.4 A resolution. It has, been refined to an R factor of 0.163 for 9044 reflections. The Lf-fragment, forms several intermolecular interactions with proteinase K. The Ser-224, Ogamma and His-57 N epsilon2 move away to a distance of 3.68 A in the, complex. In the crystal structure, Gln-3I (I indicates inhibitor i.e., lactoferrin fragment) is involved in a direct intermolecular interaction, with a symmetry related proteinase K molecule through a strong hydrogen, bond with Asp-254. The mode of intermolecular interactions in the complex, conformational features of the enzyme and placement of the fragment with, respect to the enzyme resemble with the molecular complex of proteinase K, with its natural inhibitor PKI3 from wheat.
About this StructureAbout this Structure
1BJR is a Single protein structure of sequence from Bubalus bubalis and Engyodontium album with CA as ligand. Active as Peptidase K, with EC number 3.4.21.64 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of a complex formed between proteolytically-generated lactoferrin fragment and proteinase K., Singh TP, Sharma S, Karthikeyan S, Betzel C, Bhatia KL, Proteins. 1998 Oct 1;33(1):30-8. PMID:9741842
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