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'''COMPLEX FORMED BETWEEN PROTEOLYTICALLY GENERATED LACTOFERRIN FRAGMENT AND PROTEINASE K''' | '''COMPLEX FORMED BETWEEN PROTEOLYTICALLY GENERATED LACTOFERRIN FRAGMENT AND PROTEINASE K''' | ||
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[[Category: Sharma, S.]] | [[Category: Sharma, S.]] | ||
[[Category: Singh, T P.]] | [[Category: Singh, T P.]] | ||
[[Category: | [[Category: Hydrolase]] | ||
[[Category: | [[Category: Inhibitor]] | ||
[[Category: | [[Category: Lactoferrin]] | ||
[[Category: | [[Category: Proteinase k]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:36:24 2008'' | |||
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Revision as of 11:36, 2 May 2008
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. 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 Page seeded by OCA on Fri May 2 11:36:24 2008