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oai:recercat.cat:20.500.14342/9712025-05-28T23:43:37Zcom_2072_482405com_2072_183628col_2072_482414

00925njm 22002777a 4500 dc Faijes, Magda author Val Cid, Cristina author Biarnés, Xevi author Planas, Antoni author 2015-05 Hexosaminidases are involved in important biological processes catalyzing the hydrolysis of N-acetyl-hexosaminyl residues in glycosaminoglycans and glycoconjugates. The GH20 enzymes present diverse domain organizations for which we propose two minimal model architectures: Model A containing at least a non-catalytic GH20b domain and the catalytic one (GH20) always accompanied with an extra α-helix (GH20b-GH20-α), and Model B with only the catalytic GH20 domain. The large Bifidobacterium bifidum lacto-N-biosidase was used as a model protein to evaluate the minimal functional unit due to its interest and structural complexity. By expressing different truncated forms of this enzyme, we show that Model A architectures cannot be reduced to Model B. In particular, there are two structural requirements general to GH20 enzymes with Model A architecture. First, the non-catalytic domain GH20b at the N-terminus of the catalytic GH20 domain is required for expression and seems to stabilize it. Second, the substrate-binding cavity at the GH20 domain always involves a remote element provided by a long loop from the catalytic domain itself or, when this loop is short, by an element from another domain of the multidomain structure or from the dimeric partner. Particularly, the lacto-N-biosidase requires GH20b and the lectin-like domain at the N- and C-termini of the catalytic GH20 domain to be fully soluble and functional. The lectin domain provides this remote element to the active site. We demonstrate restoration of activity of the inactive GH20b-GH20-α construct (model A architecture) by a complementation assay with the lectin-like domain. The engineering of minimal functional units of multidomain GH20 enzymes must consider these structural requirements. http://hdl.handle.net/20.500.14342/971 https://doi.org/10.1371/journal.pone.0128075 Enzims Proteïnes Lectines Proteïnes--Estructura Cristalls Protein domains Protein structure Protein structure databases Enzyme structure Enzymes Lectins Crystal structure Arginine Structural-functional analysis reveals a specific domain organization in family GH20 hexosaminidases