1J1N

Structure Analysis of AlgQ2, A Macromolecule(Alginate)-Binding Periplasmic Protein Of Sphingomonas Sp. A1., Complexed with an Alginate Tetrasaccharide

Summary for 1J1N

• Entry DOI: 10.2210/pdb1j1n/pdb
• Related: 1KWH
• Descriptor: AlgQ2, beta-D-mannopyranuronic acid-(1-4)-alpha-D-mannopyranuronic acid-(1-4)-alpha-L-gulopyranuronic acid-(1-4)-alpha-D-mannopyranuronic acid, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: alginate, sugar binding protein
• Biological source: Sphingomonas sp.
• Total number of polymer chains: 2
• Total formula weight: 116028.61

Authors

Momma, K.,Mikami, B.,Mishima, Y.,Hashimoto, W.,Murata, K. (deposition date: 2002-12-11, release date: 2003-06-10, Last modification date: 2023-10-25)

Primary citation

Mishima, Y.,Momma, K.,Hashimoto, W.,Mikami, B.,Murata, K.
Crystal structure of AlgQ2, a macromolecule (alginate)-binding protein of Sphingomonas sp. A1, complexed with an alginate tetrasaccharide at 1.6-A resolution
J.BIOL.CHEM., 278:6552-6559, 2003

PubMed Abstract: Sphingomonas sp. A1 possesses a high molecular weight (HMW) alginate uptake system composed of a novel pit formed on the cell surface and a pit-dependent ATP-binding cassette (ABC) transporter in the inner membrane. The transportation of HMW alginate from the pit to the ABC transporter is mediated by the periplasmic HMW alginate-binding proteins AlgQ1 and AlgQ2. We determined the crystal structure of AlgQ2 complexed with an alginate tetrasaccharide using an alginate-free (apo) form as a search model and refined it at 1.6-A resolution. One tetrasaccharide was found between the N and C-terminal domains, which are connected by three extended hinge loops. The tetrasaccharide complex took on a closed domain form, in contrast to the open domain form of the apo form. The tetrasaccharide was bound in the cleft between the domains through van der Waals interactions and the formation of hydrogen bonds. Among the four sugar residues, the nonreducing end residue was located at the bottom of the cleft and exhibited the largest number of interactions with the surrounding amino acid residues, suggesting that AlgQ2 mainly recognizes and binds to the nonreducing part of a HMW alginate and delivers the polymer to the ABC transporter through conformational changes (open and closed forms) of the two domains.

PubMed: 12486124
DOI: 10.1074/jbc.M209932200

Experimental method

X-RAY DIFFRACTION (1.6 Å)