The accessory domain changes the accessibility and molecular topography of the catalytic interface in monomeric GH39 ss-xylosidases

Author(s)

Santos, Camila Ramos ; Polo, Carla Cristina ; Correa, Juliana Moco ; Garcia Simao, Rita de Cassia ; Vicente Seixas, Flavio Augusto ; Murakami, Mario Tyago

• Document type: Journal article
• Source: ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY; v. 68, p. 7-pg., 2012-10-01.

Abstract

beta-Xylosidases (EC 3.2.1.37) are among the principal glycosyl hydrolases involved in the breakdown of hemicelluloses, catalyzing the reduction of xylooligosaccharides to free xylose. All GH39 beta-xylosidases structurally characterized to date display a modular multi-domain organization that assembles a tetrameric quaternary structure. In this work, the crystal structure and the SAXS molecular envelope of a new GH39 beta-xylosidase from Caulobacter crescentus (CcXynB2) have been determined. Interestingly, CcXynB2 is a monomer in solution and comparative structural analyses suggest that the shortened C-terminus prevents the formation of a stable tetramer. Moreover, CcXynB2 has a longer loop from the auxiliary domain (the long a-helix-containing loop) which makes a number of polar and hydrophobic contacts with the parental (a/beta)8-barrel domain, modifying the accessibility and the molecular topography of the catalytic interface. These interactions also maintain the accessory domain tightly linked to the catalytic core, which may be important for enzyme function and stability. (AU)

• FAPESP's process: 10/51890-8 - SMOLBnet 2.0: Structural studies of transcription factors involved in the regulation of hydrolytic enzyme genes and swollenin from Aspergillus niger and A. fumigatus
• Grantee: Mário Tyago Murakami
• Support Opportunities: Regular Research Grants