Biomedical subjects

S M Ring

Publications and source records attributed to S M Ring.

13 recordsLinked to original sources

PubMed1999

Structural studies on the effects of the deletion in the red cell anion exchanger (band 3, AE1) associated with South East Asian ovalocytosis.

We have carried out a solution-state NMR study of synthetic peptides patterned on the first membrane span of normal human band 3, and the same region of the mutant band 3 present in Southeast Asian ovalocytosis (SAO) which has a nine amino acid deletion. In 1:1 (v/v) chloroform/methanol, the 42 residue normal peptide (R389-K430) consisted of three helical regions. The slow solvent exchange of backbone amide protons revealed the helix from P403 to A416 was more stable than the "cytoplasmic" N-terminal helix from P391 to A400. These helices were separated by a sharp bend at P403, which is probably located at the boundary between the cytoplasmic domain and the first transmembrane span. The SAO deletion (A400-A408) removed the bend at P403, to leave a stable helix from P391 to A416 containing the residuum of the normal first transmembrane helix and with a hydrophobic turn replaced by a polar turn in the SAO peptide. Insertion of fragments of normal band 3 and band 3 SAO into microsomal membranes was investigated using a cell free translation system. A fragment composed of the cytoplasmic domain and the putative first membrane domain of normal band 3 (B3(1)) inserted stably into the membrane. However, the corresponding fragment of band 3 SAO [SAO(1)] did not integrate stably into membranes. Our results suggest that in SAO band 3, the region of the first membrane span of normal band 3 does not integrate properly into the membrane because it lacks a sufficiently long hydrophobic segment, and the deletion also disrupts a conserved structural subdomain at the membrane surface.

Amides↗

PubMed1999

South-east asian ovalocytic (SAO) erythrocytes have a cold sensitive cation leak: implications for in vitro studies on stored SAO red cells.

South-east Asian ovalocytosis (SAO) results from the heterozygous presence of an abnormal band 3, which causes several alterations in the properties of the erythrocytes. Although earlier studies suggested that SAO erythrocytes are refractory to invasion in vitro by the malarial parasite Plasmodium falciparum, a more recent study showed that fresh SAO cells were invaded by the parasites, but became resistant to invasion on storage because intracellular ATP was depleted more rapidly than normal. Here we show that SAO red cells are much more leaky to sodium and potassium than normal red cells when stored in the cold. This leak was much less marked when the cells were stored at 25 or 37 degreesC. Incubation for 3.5 h at 37 degreesC of cold-stored SAO red cells did not restore sodium and potassium to normal levels, probably because the depleted ATP level in cold-stored SAO red cells is further reduced with incubation at 37 degreesC. The increased leakiness of SAO red cells is non-specific and extends to calcium ions, taurine, mannitol and sucrose. These results suggest that SAO red cells undergo a structural change on cooling. Since many of the reports describing altered properties of SAO red cells have used cells which have been stored in the cold, these results need re-evaluation using never-chilled SAO red cells to assess whether the cells have the same abnormal properties under in vivo conditions.

Adenosine Triphosphate↗

PubMed1999

Glycophorin A mutation Ala65 --> Pro gives rise to a novel pair of MNS alleles ENEP (MNS39) and HAG (MNS41) and altered Wrb expression: direct evidence for GPA/band 3 interaction necessary for normal Wrb expression.

We report here a novel Glycophorin A (GPA) mutation Ala65 --> Pro which gives rise to a low-incidence antigen HAG, lack of a high-incidence antigen ENEP and aberrant expression of the high-incidence Wrb antigen. Anti-ENEP was identified in the serum of a transfused male patient (E.H.) who was homozygous for a GPA Ala65 --> Pro mutation and possessed a novel low-incidence antigen which we have called HAG. An unrelated HAG-positive individual, heterozygous for the Ala65 --> Pro mutation, has also been identified. Anti-HAG was present in several multispecific antisera to low-incidence antigens and in one monospecific serum. Normal expression of the Wrb antigen depends on the presence of amino acid Glu658 of band 3 and on the presence of GPA. However, a specific epitope on GPA has not previously been implicated. DNA sequence analysis of band 3 from patient E.H. was normal in the region of Wra/Wrb polymorphism with homozygous presence of Glu658 and therefore the abnormal Wrb expression results from the Ala65 --> Pro mutation in GPA. The ENEP and HAG antigens have been assigned the MNS blood group system numbers 002.039 and 002.041, respectively, by the ISBT Working Party on Terminology for Red Cell Surface Antigens.

Alanine↗

PubMed1998

Studies on the structure of a transmembrane region and a cytoplasmic loop of the human red cell anion exchanger (band 3, AE1).

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Amino Acid Sequence↗

PubMed1995

Changes in the blood group Wright antigens are associated with a mutation at amino acid 658 in human erythrocyte band 3: a site of interaction between band 3 and glycophorin A under certain conditions.

The Wright (Wr) blood group antigens, Wra and Wrb, have been suggested to be determined by alleles of the same gene. The Wrb antigen appears to involve both red blood cell (RBC) band 3 and glycophorin A (GPA). We have examined the cDNA sequences of the band 3 and GPA of one of the two known Wr(a+b-) individuals. We show that this individual is homozygous for the mutation Glu658-->Lys in band 3, but has normal GPA. Putative heterozygotes with Wr(a+b+) RBCs have both Glu and Lys at residue 658 of band 3, whereas the common Wr(a-b+) RBC phenotype only have band 3 with Glu658. The Wra and Wrb antigens are determined by the amino acid at residue 658 of band 3 and are antithetical. Examination of the amino acid sequence and Wrb antigen expression of GPA-related hybrid glycophorins suggests that Arg61 of GPA interacts with Glu658 of band 3 to form the Wrb antigen. We suggest that the interaction is stabilized by the presence of anti-Wrb antibodies and that this site of association between GPA and band 3 may be responsible for the previously reported ability of anti-GPA antibodies to decrease the deformability of RBCs.

Alleles↗

PubMed1994

Production of a murine monoclonal antibody to the low-incidence red cell antigen Wra: characterisation and comparison with human anti-Wra.

The production of a monoclonal antibody which detects the low-incidence red cell antigen Wra is described. The antibody (BGU1-WR) was isolated following immunization of BALB/tk mice with Wr(a+) cells. BGU1-WR is an IgG1 antibody and reacted in a manner similar to human polyclonal anti-Wra with untreated, protease treated and chemically modified Wr(a+) cells.

Animals↗

PubMed1994

Comparative immunochemical analysis of Wra and Wrb red cell antigens.

This paper describes immunoblotting and immunoprecipitation studies using monoclonal anti-Wra and anti-Wrb antibodies to investigate the nature of the low-incidence blood group antigen, Wra and its high-incidence allelic antigen Wrb. No membrane components were identified by the immunoblotting experiments. Immunoprecipitation studies confirmed that the Wrb antigen involves both glycophorin A and band 3. The monoclonal anti-Wra, BGU1-WR, failed to immunoprecipitate these or any othe red cell membrane component. The significance of these findings is discussed.

Alleles↗

PubMed1993

The expression of the abnormal human red cell anion transporter from South-East Asian ovalocytes (band 3 SAO) in Xenopus oocytes.

South-East Asian ovalocytosis (SAO) is caused by the heterozygous presence of a variant form of the human erythrocyte anion transporter (band 3; AE1). The expression of band 3 SAO has been studied in Xenopus oocytes. Band 3 SAO is not functional as an anion transporter but is inserted stably into the plasma membrane of oocytes. Band 3 SAO translocation to the cell surface does not require co-expression of normal band 3. Co-expression of glycophorin A (GPA) increases the rate of translocation of band 3 SAO to the oocyte membrane but is not essential for this process. We suggest that the increased tendency of band 3 SAO to form oligomers may facilitate its translocation to the cell surface.

Animals↗

PubMed1972