The Hexopyranosyl Residue That Is C-Glycosidically Linked to the Side Chain of Tryptophan-7 in Human RNase Us Is .alpha.-Mannopyranose

Vliegenthart, J.F.G.; Beer, Tonny de; Löffler, Andreas; Hofsteenge, Jan

doi:10.1021/bi00037a016

Cited by 113 publications

(98 citation statements)

References 31 publications

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“…An additional anomeric track is located at 5.23 ppm. The cross-peak patterns on this anomeric track in 1 H NOE and 1 H TOCSY spectra of denatured RNase 2, as well as the locations of these cross-peaks, are similar to those of the Man H1′ tracks in 1 H ROE 5 and 1 H TOCSY spectra of C-linked Man in FT-(C 2 -Man-)WAQW [ Figure 3 and Hofsteenge et al (1994) and de Beer et al (1995)]. This includes the typical, intense NOE/ROE 5 cross-peak that indicates that Man H1′ and Man H6′ are close in space (Figure 3).…”

Section: Stability Of the O-mannosylated Syntheticmentioning

confidence: 65%

“…Recently, it was found that Trp-7 in human RNase 2 1 is modified by C-glycosidic attachment of an R-mannosyl residue (Hofsteenge et al, 1994;de Beer et al, 1995). In contrast to the previously known N-and O-glycosidic linkages to asparagine and serine, or threonine, the mannopyranosyl C1′ atom is in this case directly linked to the C2 atom of the tryptophan indole ring.…”

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confidence: 88%

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Spectroscopic and Protein Chemical Analyses Demonstrate the Presence of C-Mannosylated Tryptophan in Intact Human RNase 2 and Its Isoforms

et al. 1996

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Recently, the C-mannosylation of a specific tryptophan residue in RNase 2 from human urine has been reported [Hofsteenge, J., et al. (1994) Biochemistry 33, 13524-13530; de Beer, T., et al. (1995) Biochemistry 34, 11785-11789]. In those studies, identification of this unusual modification was accomplished by mass spectrometric and NMR spectroscopic analysis of peptide fragments. The evidence for the occurrence of C 2 -R-mannosyltryptophan [(C 2 -Man-)Trp] in the intact protein relied exclusively on the detection of the same phenylthiohydantoin derivatives during Edman degradation. In this paper, we have (1) excluded the possibility that (C 2 -Man-)Trp arose artificially under the acidic conditions previously employed for protein and peptide isolation and analysis, by maintaining the pH >5 throughout these procedures, (2) demonstrated the occurrence of (C 2 -Man-)Trp in the intact protein, by NMR spectroscopy, (3) showed that (C 2 -Man-)Trp is not unique for RNase 2 from urine but that it is also present in the enzyme isolated from erythrocytes, and (4) found also that high-molecular mass isoforms of urinary RNase 2 are C-mannosylated. These observations firmly establish C-mannosylation as a novel way of posttranslationally attaching carbohydrate to protein, in addition to the well-known N-and O-glycosylations. Furthermore, the NMR data, in combination with molecular dynamics calculations, indicate that in the native protein the mannopyranosyl residue is in a different conformation than in the glycopeptide or denatured protein, due to protein-carbohydrate interactions.

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Section: Stability Of the O-mannosylated Syntheticmentioning

confidence: 65%

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confidence: 88%

Spectroscopic and Protein Chemical Analyses Demonstrate the Presence of C-Mannosylated Tryptophan in Intact Human RNase 2 and Its Isoforms

et al. 1996

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“…The EGF domains appear to be more compact and less flexible in C8 than in EGF, as judged by a greater similarity between C8␣ and C8␤ EGF domains (root mean square displacement of 1.7 Å, based on C␣ atoms of 30 residues) than between two copies of EGF proteins in the unit cell in their crystal structure (root mean square displacement of 3.3 Å; based on C␣ atoms of 24 residues) (36 Post-translational Modifications-An infrequent modification of proteins is the covalent attachment of a mannopyranosyl moiety to C␦1 of tryptophan via a C-C bond. NMR studies of a peptide derived from mannosylated human RNase indicated that an ␣-mannopyranose is attached (37). However, thus far there is no reported crystal structure of a peptide or protein containing a mannosyl tryptophan.…”

Section: Resultsmentioning

confidence: 99%

Structure of Human C8 Protein Provides Mechanistic Insight into Membrane Pore Formation by Complement

Lovelace

Cooper

Sodetz

et al. 2011

Journal of Biological Chemistry

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C8 is one of five complement proteins that assemble on bacterial membranes to form the lethal pore-like "membrane attack complex" (MAC) of complement. The MAC consists of one C5b, C6, C7, and C8 and 12-18 molecules of C9. C8 is composed of three genetically distinct subunits, C8␣, C8␤, and C8␥. The C6, C7, C8␣, C8␤, and C9 proteins are homologous and together comprise the MAC family of proteins. All contain N-and C-terminal modules and a central 40-kDa membrane attack complex perforin (MACPF) domain that has a key role in forming the MAC pore. Here, we report the 2.5 Å resolution crystal structure of human C8 purified from blood. This is the first structure of a MAC family member and of a human MACPF-containing protein. The structure shows the modules in C8␣ and C8␤ are located on the periphery of C8 and not likely to interact with the target membrane. The C8␥ subunit, a member of the lipocalin family of proteins that bind and transport small lipophilic molecules, shows no occupancy of its putative ligand-binding site. C8␣ and C8␤ are related by a rotation of ϳ22°with only a small translational component along the rotation axis. Evolutionary arguments suggest the geometry of binding between these two subunits is similar to the arrangement of C9 molecules within the MAC pore. This leads to a model of the MAC that explains how C8-C9 and C9-C9 interactions could facilitate refolding and insertion of putative MACPF transmembrane ␤-hairpins to form a circular pore. Assembly of the "membrane attack complex" (MAC)3 of complement on the surface of Gram-negative bacteria and other pathogenic organisms involves the sequential interaction of complement proteins C5b, C6, C7, C8, and C9 (1-3). Association of the first four components produces a membranebound tetrameric C5b-8 complex, which then initiates the recruitment and sequential binding of 12-18 C9 molecules to form a cylindrical transmembrane pore (supplemental Fig. S1). Pore formation leads to loss of membrane integrity and lysis of the cell under attack.The sequence of interactions leading to MAC formation is well defined; however, the mechanism by which the MAC disrupts membrane organization is poorly understood. C6, C7, the C8␣ and C8␤ subunits, and C9 are homologous and together comprise the "MAC family" of proteins (4, 5). Until now, structures have not been determined for any of these proteins. All contain N-and C-terminal modules and a central 40-kDa "membrane attack complex/perforin" (MACPF) domain. The MACPF domain was named as such because of sequence similarity between the MAC family proteins and perforin. The modules range in number from three to eight; all are small domains of 40 -60 amino acids that contain multiple disulfide bonds (supplemental Fig. S2). One type of module, thrombospondin type 1 (TSP1), contains several mannosylated tryptophans (6).Several hundred MACPF-containing proteins have been identified; however, functions are known for only a few. MACPF proteins exhibit limited sequence similarity, but all contain the MACPF signature motif ((Y/...

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“…Recently, a ncw type of glycosylatinn, namclx, C-mannosylation, has bccn obserxcd in human RNase 2 (formerly RNasc ['s) [1,21. The anomeric carbon atom of an a-DmannolLvranosc residue is dircctlv linked to the C2 atom of "l'rp7 {Figurc 1).…”

Section: C-glycosylationmentioning

confidence: 99%

Novel forms of protein glycosylation

Hayes

Hart

1994

Current Opinion in Structural Biology

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A large number of new glycans, derived from glycoproteins, has been characterized in the past few years. O-linked fucose was found in epidermal growth factor-like domains of several proteins. For the N-linked glycans of Helix pomatia hemocyanin, novel types of antennae were identified. The positions of noncarbohydrate substituents were established in N-glycans. C-mannosylation of a tryptophan residue was discovered in human ribonuclease 2 and is the first example of C-glycosylation in glycoproteins. Addresses

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The Hexopyranosyl Residue That Is C-Glycosidically Linked to the Side Chain of Tryptophan-7 in Human RNase Us Is .alpha.-Mannopyranose

Cited by 113 publications

References 31 publications

Spectroscopic and Protein Chemical Analyses Demonstrate the Presence of C-Mannosylated Tryptophan in Intact Human RNase 2 and Its Isoforms

Spectroscopic and Protein Chemical Analyses Demonstrate the Presence of C-Mannosylated Tryptophan in Intact Human RNase 2 and Its Isoforms

Structure of Human C8 Protein Provides Mechanistic Insight into Membrane Pore Formation by Complement

Novel forms of protein glycosylation

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