Accessibility and mobility of lysine residues in. beta. -lactoglobulin
N/sup epsilon/-(/sup 2/H/sub 6/)Isopropyllysyl-..beta..-lactoglobulin was prepared by reductive alkylation of ..beta..-lactoglobulin with (/sup 2/H/sub 6/)acetone and NaBH/sub 4/ to provide a /sup 2/H (NMR) probe for the study of lysine involvement in lipid-protein interactions. Amino acid analysis showed 80% of the protein's 15 lysine residues to be labeled. Unmodified lysine residues were located through peptide maps produced from CNBr, tryptic, and chymotryptic digests of the labeled protein. Average correlation times calculated from /sup 2/H NMR spectra were 20 and 320 ps for 8.7 and 3.3 residues, respectively, in 6 M guanidine hydrochloride; in nondenaturing solution, values of 70 and 320 ps were obtained for 6.5 and 3.2 residues, respectively, with the remaining 2.3 modified residues not observed, suggesting that side chains of lysine residues in unordered or flexible regions were more mobile than those in stable periodic structures. /sup 2/H NMR spectra of the protein complexed with dipalmitoylphosphatidylcholine confirmed the extrinsic membrane protein type behavior of ..beta..-lactoglobulin previously reported from /sup 31/P NMR studies of the phospholipids complexed with ..beta..-lactoglobulin. Although no physiological function has yet been identified, comparison of these results with the X-ray structure supports the hypothesis that residues not accessible for modification may help to stabilize the cone-shaped ..beta..-barrel thought to contain binding sites for small lipid-soluble molecules.
- Research Organization:
- Dept. of Agriculture, Philadelphia, PA (USA)
- OSTI ID:
- 7001557
- Journal Information:
- Biochemistry; (United States), Vol. 27:15
- Country of Publication:
- United States
- Language:
- English
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GLOBULINS
AMINO ACID SEQUENCE
NUCLEAR MAGNETIC RESONANCE
LYSINE
BIOCHEMISTRY
ACETONE
ALKYLATION
CATTLE
DEUTERIUM COMPOUNDS
ELECTROPHORESIS
LIPIDS
LIQUID COLUMN CHROMATOGRAPHY
MILK
NMR SPECTRA
PHOSPHORUS 31
THIN-LAYER CHROMATOGRAPHY
WHEY
AMINO ACIDS
ANIMALS
BIOLOGICAL MATERIALS
BODY FLUIDS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
CHROMATOGRAPHY
DOMESTIC ANIMALS
FOOD
HYDROGEN COMPOUNDS
INDUSTRIAL WASTES
ISOTOPES
KETONES
LIGHT NUCLEI
MAGNETIC RESONANCE
MAMMALS
MATERIALS
MOLECULAR STRUCTURE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOSPHORUS ISOTOPES
PROTEINS
RESONANCE
RUMINANTS
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
VERTEBRATES
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550601* - Medicine- Unsealed Radionuclides in Diagnostics