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Preparation and partial structural characterization of alpha1T-glycoprotein from normal human plasma
T Araki1, H Haupt, P Hermentin
1School of Agriculture, Kyushu Tokai, University, Kumamoto, Aso, 869-1404, Japan. taraki@as-1.ktokai-u.ac.jp
Archives of Biochemistry and Biophysics
|April 29, 1998
Summary
Alpha-1T-glycoprotein (alpha1T), a protein found in human plasma, shares significant sequence homology with albumin proteins. This study reveals alpha1T possesses five unique N-glycans, distinguishing it within the albumin family.
Area of Science:
- Biochemistry
- Proteomics
- Glycobiology
Background:
- Alpha-1T-glycoprotein (alpha1T) is a protein isolated from normal human plasma.
- Understanding its structure and relation to other plasma proteins is crucial.
Purpose of the Study:
- To determine the partial amino acid sequence and carbohydrate chains of alpha1T.
- To compare alpha1T's sequence with other known proteins, particularly within the albumin family.
Main Methods:
- Isolation of immunochemically homogeneous alpha1T from human plasma.
- Analysis of carboxymethylated alpha1T using various protease digestions (lysylendoprotease, V8 protease, tryptic) and cyanogen bromide peptide sequencing.
- N-terminal sequencing and chemical determination of amino acid residues.
Main Results:
- A significant portion of the alpha1T amino acid sequence (460 residues) was determined.
- High sequence homology was observed between alpha1T and proteins of the albumin family.
- Human alpha-albumin exhibits an identical amino acid sequence to alpha1T, indicating close similarity.
- Five N-glycan chains were identified on alpha1T at specific asparagine residues (Asn12, Asn88, Asn362, Asn381, Asn467).
- The N-glycan at Asn362 features a rare Asn-X-Cys consensus sequence.
Conclusions:
- Alpha1T is closely related to alpha-fetoprotein and human alpha-albumin, belonging to the albumin protein family.
- The presence of five N-glycans is a novel finding for alpha1T and distinguishes it within the ALB family.