Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.1.14 (SPS)
 813 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 40kDa glycoprotein from dry secretion of sheep is implicated as a signaling factor and is named as SPS-40. This protein is secreted only during the early phase of involution when the drastic tissue remodeling occurs in the mammary gland. SPS-40 was purified from sheep dry secretions and crystallized using hanging drop vapour diffusion method. The crystals belong to orthorhombic space group P2(1)2(1)2(1) with cell dimensions, a=62.7A, b=66.4A, c=107.5A. The protein was also cloned for the determination of its complete amino acid sequence. The three-dimensional structure of SPS-40 was determined by X-ray crystallographic method at 2.0A resolution. The structure revealed the presence of an N-linked glycan chain at Asn39. The protein adopts a conformation with a classical (beta/alpha)(8)-barrel fold of triosephosphate isomerase (TIM) (residues 1-237 and 310-360) with an insertion of a small (alpha+beta) domain (residues 240-307) similar to that observed in chitinases. However, the Leu substitution for Glu in the consensus catalytic sequence in SPS-40 causes a loss of chitinase activity. Furthermore, the sugar-binding groove in SPS-40 is distorted considerably from the standard chitin-binding site in chitinase enzymes and hence the binding of chitin-like oligosaccharides is considerably hampered. Three surface loops, His188-His197, Phe202-Arg212 and Phe244-Pro260 have exceptionally high values of B-factors (average=70.5A(2)), indicating the presence of a less defined region.
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PMID:Crystal structure of a secretory signalling glycoprotein from sheep at 2.0A resolution. 1685 26

Crystal structures of four complexes of sheep secretory glycoprotein (SPS-40) with N-acetylglucosamine oligosaccharides (GlcNAc(n), (n=3-6)) have been determined at moderate resolutions. The binding studies of SPS-40 have been carried out using fluorescence spectroscopy and Surface Plasmon Resonance (SPR). Structure determinations of four complexes have shown a novel binding pattern of GlcNAc(n) molecules to SPS-40. The results indicate that the most preferred recognition region in the carbohydrate binding groove in SPS-40 is at subsites -4 to -2 among which subsite -2 provides the maximum interactions with carbohydrate residues. These structures have also shown that the interactions of GlcNAc3 and GlcNAc4 do not perturb the protein structure and those of GlcNAc5 induce partial conformational changes while in the case of GlcNAc6 the partially closed binding groove opened up completely. As in other SPX-40 structures, SPS-40 structure contains three overlapping flexible surface segments, His188-His197, Phe202-Arg212 and Phe244-Pro260 with several charged residues protruding outwardly. It creates a cluster of positive charges with a flexible base thus indicating a good scope of promoting the intermolecular interactions. This protein is glycosylated at Asn39 and may recognize other receptors having sugar binding sites. It appears that SPS-40 may involve both carbohydrate and protein bindings. The systematic carbohydrate-binding studies and the detailed structural results of four protein-carbohydrate complexes provide an excellent insight into the mechanism of carbohydrate binding. These are the first studies of this kind on secretory glycoproteins and their interactions with carbohydrates.
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PMID:Carbohydrate binding properties and carbohydrate induced conformational switch in sheep secretory glycoprotein (SPS-40): crystal structures of four complexes of SPS-40 with chitin-like oligosaccharides. 1718 13

The 40 kDa secretory signalling glycoprotein (SPS-40) is the first example with Trp78 in three functional orientations: (i) a resting state with a pinched conformation, (ii) a stacked conformation when bound to hexasaccharide and (iii) an obstructive conformation when inhibited by 2-methylpentane-2,4-diol (MPD). Trp78 is present in the core of the sugar-binding groove. The hexasaccharide N-acetylglucosamine (GlcNAc(6)) has been shown to bind to SPS-40. As a result of this, the conformation of Trp78 alters from the native pinched conformation (chi(1) = -65.5 degrees , chi(2,1) = -78.8 degrees , chi(2,2) = 97.5 degrees ) to the stacked conformation (chi(1) = -170.0 degrees , chi(2,1) = -114.3 degrees , chi(2,2) = 61.6 degrees ). Further binding experiments showed that saccharide binding does not occur in the presence of 20% MPD. The crystal structure determination of the complex of SPS-40 with MPD revealed the presence of two MPD molecules in the sugar-binding groove. The very tightly bound MPD molecules at subsites -2 and -1 induced an unexpected and a rarely observed conformation of Trp78 (chi(1) = 55.9 degrees , chi(2,1) = 90.2 degrees , chi(2,2) = -88.9 degrees ) which is termed an obstructive conformation. The binding of MPD molecules also twisted the side chains of Glu269 and Ile272 considerably. These residues are also part of the sugar-binding groove. The observed obstructive conformation of the side chain of Trp78 in the present structure is the exact opposite of the stacked conformation. This rarely observed conformation is stabilized by a number of hydrogen bonds between Trp78 and Asn79 through water molecules W49, W229, W269, W547 and W557.
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PMID:Tryptophan as a three-way switch in regulating the function of the secretory signalling glycoprotein (SPS-40) from mammary glands: structure of SPS-40 complexed with 2-methylpentane-2,4-diol at 1.6 A resolution. 1930 19