Identification and synthesis of a novel 15 kDa beta-galactoside-binding lectin in human leukocytes.
Knowledge of the identity, synthesis and secretion of beta-galactoside-binding lectins by leukocytes is of importance because lactosaminoglycans present at the leukocyte cell surface may be physiologically significant lectin receptors that could mediate autocrine or paracrine functions and/or cell adhesion. This paper presents data that show that a previously identified 15.5-16.5 kDa lactose-binding protein synthesized in vitro by human peripheral leukocytes is actually comprised of three different polypeptides. One of these is related to a novel 15 kDa lectin isolated from human spleen and which is synthesized by B lymphoblastoid cells. Spleen contains at least six lactose-binding polypeptides for which the carbohydrate-binding activity is independent of the presence of divalent cations and mercaptoethanol. The splenic 15 kDa polypeptide does not appear to be immunologically related to previously characterized beta-galactoside-binding lectins. It is separable from galaptin, another galactoside-binding lectin (subunit mol. wt 14.5 kDa) by chromatography on DEAE-Sephacel. Western blot analyses and immunoprecipitation/fluorography experiments with metabolically labelled cells showed the presence of the 15 kDa lectin in peripheral leukocytes and in Epstein-Barr virus-immortalized B lymphoblastoid cells. The 15 kDa lectin yielded polypeptide fragments of approximately 6.2 and approximately 8.6 kDa after cyanogen bromide (CNBr) degradation. These fragments were partially sequenced and 12 residues/fragment were identified. A similarity search of the SWISS PROT protein data base did not reveal a relationship of the 15 kDa polypeptide to known lectins, including galaptin.(ABSTRACT TRUNCATED AT 250 WORDS)
Sharma
A
A
Department of Gynecologic Oncology, Roswell Park Cancer Institute, Buffalo, NY 14263.
DiCioccio
R A
RA
Allen
H J
HJ
D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000378:metabolism; D015153:Blotting, Western; D003488:Cyanogen Bromide; D004591:Electrophoresis, Polyacrylamide Gel; D037161:Galectins; D006388:Hemagglutinins / Q000096:biosynthesis / Q000097:blood* / Q000737:chemistry; D006801:Humans; D007163:Immunosorbent Techniques; D007962:Leukocytes / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D013154:Spleen / Q000737:chemistry
D037161:Galectins; D006388:Hemagglutinins; D010446:Peptide Fragments; D003488:Cyanogen Bromide