X-Ray diffraction study on (1→3)-α-d-mannan dihydrate
1986; Elsevier BV; Volume: 148; Issue: 1 Linguagem: Inglês
10.1016/0008-6215(86)80042-8
ISSN1873-426X
AutoresKozo Ogawa, Toshio Miyanishi, Toshifumi Yui, Chihiro Hara, Tadashi Kiho, Shigeo Ukai, A. Sarko,
Tópico(s)Glycosylation and Glycoproteins Research
ResumoThe most distinctive feature of the human pathogenic fungus is a polysaccharide capsule that is essential for virulence and is composed primarily of glucuronoxylomannan (GXM) and galactoxylomannan (GalXM). GXM mediates multiple deleterious effects on host immune function, yet relatively little is known about its physical properties. The average mass of Cryptococcus neoformans GXM from four antigenically different strains ranged from 1.7 to 7 × 106 daltons as calculated from Zimm plots of light-scattering data. GalXM was significantly smaller than GXM, with an average mass of 1 × 105 daltons. These molecular masses imply that GalXM is the most numerous polysaccharide in the capsule on a molar basis. The radius of gyration of the capsular polysaccharides ranged between 68 and 208 nm. Viscosity measurements suggest that neither polysaccharide altered fluid dynamics during infection since GXM behaved in solution as a polyelectrolyte and GalXM did not increase solution viscosity. Immunoblot analysis indicated heterogeneity within GXM. In agreement with this, scanning transmission electron microscopy of GXM preparations revealed a tangled network of two different types of molecules. Mass per length measurements from light scattering and scanning transmission electron microscopy were consistent and suggested GXM molecules self-associate. A mechanism for capsule growth is proposed based on the extracellular release and entanglement of GXM molecules.
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