1BJR

COMPLEX FORMED BETWEEN PROTEOLYTICALLY GENERATED LACTOFERRIN FRAGMENT AND PROTEINASE K

Summary for 1BJR

• Entry DOI: 10.2210/pdb1bjr/pdb
• Descriptor: PROTEINASE K, LACTOFERRIN, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: proteinase k, lactoferrin, iron transport, hydrolase-hydrolase inhibitor complex, hydrolase/hydrolase inhibitor
• Biological source: Engyodontium album; More
• Total number of polymer chains: 2
• Total formula weight: 29824.84

Authors

Singh, T.P.,Sharma, S.,Karthikeyan, S.,Betzel, C.,Bhatia, K.L. (deposition date: 1998-06-27, release date: 1998-11-04, Last modification date: 2024-11-20)

Primary citation

Singh, T.P.,Sharma, S.,Karthikeyan, S.,Betzel, C.,Bhatia, K.L.
Crystal structure of a complex formed between proteolytically-generated lactoferrin fragment and proteinase K.
Proteins, 33:30-38, 1998

PubMed Abstract: 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.

PubMed: 9741842
DOI: 10.1002/(SICI)1097-0134(19981001)33:1<30::AID-PROT3>3.3.CO;2-W

Experimental method

X-RAY DIFFRACTION (2.44 Å)