Biosynthesis of human sialophorins and analysis of the polypeptide core

Journal Article · Tue Jun 30 00:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00387a025· OSTI ID:5842105

Remold-O'Donnell, E; Kenney, D; Rosen, F S

Biosynthesis was examined of sialophorin (formerly called gpL115) which is altered in the inherited immunodeficiency Wiskott-Aldrich syndrome. Sialophorin is greater than 50% carbohydrate, primarily O-linked units of sialic acid, galactose, and galactosamine. Pulse-labeling with (/sup 35/S)methionine and chase incubation established that sialophorin is synthesized in CEM lymphoblastoid cells as an Mr 62,000 precursor which is converted within 45 min to mature glycosylated sialophorin, a long-lived molecule. Experiments with tunicamycin and endoglycosidase H demonstrated that sialophorin contains N-linked carbohydrate (approximately two units per molecule) and is therefore an N,O-glycoprotein. Pulse-labeling of tunicamycin-treated CEM cells together with immunoprecipitation provided the means to isolate the (/sup 35/S)-methionine-labeled polypeptide core of sialophorin and determine its molecular weight (58,000). This datum allowed us to express the previously established composition on a per molecule basis and determine that sialophorin molecules contain approximately 520 amino acid residues and greater than or equal to 100 O-linked carbohydrate units. A recent study showed that various blood cells express sialophorin and that there are two molecular forms: lymphocyte/monocyte sialophorin and platelet/neutrophil sialophorin. Biosynthesis of the two forms was compared by using sialophorin of CEM cells and sialophorin of MOLT-4 cells (another lymphoblastoid line) as models for lymphocyte/monocyte sialophorin and platelet/neutrophil sialophorin, respectively. The time course of biosynthesis and the content of N units were found to be identical for the two sialophorin species. (/sup 35/S)Methionine-labeled polypeptide cores of CEM sialophorin and MOLT sialophorin were isolated and compared by electrophoresis, isoelectrofocusing, and a newly developed peptide mapping technique.

• Research Organization: The Children's Hospital, Boston, MA
• OSTI ID: 5842105
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:13; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOSYNTHESIS
CARBOHYDRATES
CARBOXYLIC ACIDS
CHEMICAL COMPOSITION
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTROPHORESIS
EVEN-ODD NUCLEI
GLUCOPROTEINS
IMMUNOASSAY
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
METHIONINE
MOLECULAR WEIGHT
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PEPTIDES
PROTEINS
RADIOISOTOPES
SACCHARIDES
SULFUR 35
SULFUR ISOTOPES
SYNTHESIS
TRACER TECHNIQUES