A unique GCN5-related glucosamine N-acetyltransferase region exist in the fungal multi-domain glycoside hydrolase family 3 β-N-acetylglucosaminidase.

Zhen Qin,Jeroen R Mesters,Xinbin Yang,Yibei Xiao,Zhengqiang Jiang,Shaoqing Yang

doi:10.1038/srep18292

Abstract

Glycoside hydrolase (GH) family 3 β-N-acetylglucosaminidases widely exist in the filamentous fungi, which may play a key role in chitin metabolism of fungi. A multi-domain GH family 3 β-N-acetylglucosaminidase from Rhizomucor miehei (RmNag), exhibiting a potential N-acetyltransferase region, has been recently reported to show great potential in industrial applications. In this study, the crystal structure of RmNag was determined at 2.80 Å resolution. The three-dimensional structure of RmNag showed four distinctive domains, which belong to two distinguishable functional regions — a GH family 3 β-N-acetylglucosaminidase region (N-terminal) and a N-acetyltransferase region (C-terminal). From structural and functional analysis, the C-terminal region of RmNag was identified as a unique tandem array linking general control non-derepressible 5 (GCN5)-related N-acetyltransferase (GNAT), which displayed glucosamine N-acetyltransferase activity. Structural analysis of this glucosamine N-acetyltransferase region revealed that a unique glucosamine binding pocket is located in the pantetheine arm binding terminal region of the conserved CoA binding pocket, which is different from all known GNAT members. This is the first structural report of a glucosamine N-acetyltransferase, which provides novel structural information about substrate specificity of GNATs. The structural and functional features of this multi-domain β-N-acetylglucosaminidase could be useful in studying the catalytic mechanism of GH family 3 proteins.

Highlights

Glucosamine N-acetyltransferase (EC 2.3.1.3) catalyses the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to a glucosamine (GlcN) acceptor generating a N-acetylglucosamine
The full-length β -N-acetylglucosaminidase (RmNag) from Rhizomucor miehei belongs to glycoside hydrolase (GH) family 3 in the CAZy classification of carbohydrate-active enzymes[15] and the characterisation of which has been reported in our previous study[16]
The β -N-acetylglucosaminidase region (NTR) and the N-acetyltransferase region (CTR) are monomeric and dimeric in solution, respectively, indicating that full-length RmNag dimerizes via the interactions owing to its C-terminal region (CTR)

Summary

Introduction

Glucosamine N-acetyltransferase (EC 2.3.1.3) catalyses the transfer of an acetyl group from AcCoA to a glucosamine (GlcN) acceptor generating a N-acetylglucosamine. Several structures of bacterial homologues of the glycoside hydrolase domains, involved in bacterial cell wall turnover, spore germination, and induction of β -lactamase, have been determined[17]. These structures have been beneficial to design and analyse the inhibitors of GH family 3 β -N-acetylglucosaminidases[17]. Our results present new information on the GCN5-related N-acetyltransferase family, and provide a new assembly of a muti-domain β -N-acetylglucosaminidase This is the first report on a crystal structure of a fungal GH family 3 β -N-acetylglucosaminidase, representing a significant advance in our understanding of these enzymes

Methods

Results

Conclusion