Expression, purification, and characterization of avian Thy-1 from Lec1 mammalian and Tn5 insect cells

Enhanced production and isotope enrichment of recombinant glycoproteins produced in cultured mammalian cells

NMR studies of post-translationally modified proteins are complicated by the lack of an efficient method to produce isotope enriched recombinant proteins in cultured mammalian cells. We show that reducing the glucose concentration and substituting glutamate for glutamine in serum-free medium increased cell viability while simultaneously increasing recombinant protein yield and the enrichment of non-essential amino acids compared to culture in unmodified, serum-free medium. Adding dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, further improves cell viability, recombinant protein yield, and isotope enrichment. We demonstrate the method by producing partially enriched recombinant Thy1 glycoprotein from Lec1 Chinese hamster ovary (CHO) cells using U-¹³C-glucose and ¹⁵N-glutamate as labeled precursors. This study suggests that uniformly ¹⁵N,¹³C-labeled recombinant proteins may be produced in cultured mammalian cells starting from a mixture of labeled essential amino acids, glucose, and glutamate.

The 1.9 a structure of human alpha-N-acetylgalactosaminidase: The molecular basis of Schindler and Kanzaki diseases

alpha-N-acetylgalactosaminidase (alpha-NAGAL; E.C. 3.2.1.49) is a lysosomal exoglycosidase that cleaves terminal alpha-N-acetylgalactosamine residues from glycopeptides and glycolipids. In humans, a deficiency of alpha-NAGAL activity results in the lysosomal storage disorders Schindler disease and Kanzaki disease. To better understand the molecular defects in the diseases, we determined the crystal structure of human alpha-NAGAL after expressing wild-type and glycosylation-deficient glycoproteins in recombinant insect cell expression systems. We measured the enzymatic parameters of our purified wild-type and mutant enzymes, establishing their enzymatic equivalence. To investigate the binding specificity and catalytic mechanism of the human alpha-NAGAL enzyme, we determined three crystallographic complexes with different catalytic products bound in the active site of the enzyme. To better understand how individual defects in the alpha-NAGAL glycoprotein lead to Schindler disease, we analyzed the effect of disease-causing mutations on the three-dimensional structure.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.

An economic approach to isotopic enrichment of glycoproteins expressed from Sf9 insect cells

It is estimated that over half of all proteins are glycosylated, yet only a small number of the structures in the protein data bank are of intact glycoproteins. One of the reasons for the lack of structural information on glycoproteins is the high cost of isotopically labeling proteins expressed from eukaryotic cells such as in insect and mammalian cells. In this paper we describe modifications to commercial insect cell growth medium that reduce the cost for isotopically labeling recombinant proteins expressed from Sf9 cells. A key aspect of this work was to reduce the amount of glutamine in the cell culture medium while maintaining sufficient energy yielding metabolites for vigorous growth by supplementing with glucose and algae-derived amino acids. We present an analysis of cell growth and protein production in Sf9 insect cells expressing secreted Thy1-GFP fusion construct. We also demonstrate isotopic enrichment of the Thy-1 protein backbone with 15N and carbohydrates with 13C by NMR spectroscopy.