4WA0

The structure of a possible adhesin C-terminal domain from Caldicellulosiruptor kronotskyensis

Summary for 4WA0

• Entry DOI: 10.2210/pdb4wa0/pdb
• Descriptor: possible adhesin, MAGNESIUM ION (3 entities in total)
• Functional Keywords: beta-helix, caldicellulosiruptor, cell adhesion
• Biological source: Caldicellulosiruptor kronotskyensis
• Total number of polymer chains: 1
• Total formula weight: 38400.20

Authors

Alahuhta, P.M.,Lunin, V.V. (deposition date: 2014-08-28, release date: 2015-03-04, Last modification date: 2024-11-20)

Primary citation

Blumer-Schuette, S.E.,Alahuhta, M.,Conway, J.M.,Lee, L.L.,Zurawski, J.V.,Giannone, R.J.,Hettich, R.L.,Lunin, V.V.,Himmel, M.E.,Kelly, R.M.
Discrete and Structurally Unique Proteins (Tapirins) Mediate Attachment of Extremely Thermophilic Caldicellulosiruptor Species to Cellulose.
J.Biol.Chem., 290:10645-10656, 2015

PubMed Abstract: A variety of catalytic and noncatalytic protein domains are deployed by select microorganisms to deconstruct lignocellulose. These extracellular proteins are used to attach to, modify, and hydrolyze the complex polysaccharides present in plant cell walls. Cellulolytic enzymes, often containing carbohydrate-binding modules, are key to this process; however, these enzymes are not solely responsible for attachment. Few mechanisms of attachment have been discovered among bacteria that do not form large polypeptide structures, called cellulosomes, to deconstruct biomass. In this study, bioinformatics and proteomics analyses identified unique, discrete, hypothetical proteins ("tāpirins," origin from Māori: to join), not directly associated with cellulases, that mediate attachment to cellulose by species in the noncellulosomal, extremely thermophilic bacterial genus Caldicellulosiruptor. Two tāpirin genes are located directly downstream of a type IV pilus operon in strongly cellulolytic members of the genus, whereas homologs are absent from the weakly cellulolytic Caldicellulosiruptor species. Based on their amino acid sequence, tāpirins are specific to these extreme thermophiles. Tāpirins are also unusual in that they share no detectable protein domain signatures with known polysaccharide-binding proteins. Adsorption isotherm and trans vivo analyses demonstrated the carbohydrate-binding module-like affinity of the tāpirins for cellulose. Crystallization of a cellulose-binding truncation from one tāpirin indicated that these proteins form a long β-helix core with a shielded hydrophobic face. Furthermore, they are structurally unique and define a new class of polysaccharide adhesins. Strongly cellulolytic Caldicellulosiruptor species employ tāpirins to complement substrate-binding proteins from the ATP-binding cassette transporters and multidomain extracellular and S-layer-associated glycoside hydrolases to process the carbohydrate content of lignocellulose.

PubMed: 25720489
DOI: 10.1074/jbc.M115.641480

Experimental method

X-RAY DIFFRACTION (1.7 Å)