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Y Burstein

Publications and source records attributed to Y Burstein.

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PubMed1977

Amino acid sequence of the NH2-terminal extra piece segments of the precursors of mouse immunoglobulin lambda1-type and kappa-type light chains.

The mRNA molecules coding for mouse immunoglobulin light (L) chains direct the cell-free synthesis of precursors in which extra peptide segments precede the amino termini of the mature proteins. The results of amino acid sequence analyses of two precursors labeled with 20 radioactive amino acids enabled unambiguous determination of the complete primary structure of the extra piece segments. The complete sequences (and sizes) of the NH2-terminal extra pieces are: in MOPC-104E lambda1 L-chain precursor, Met-Ala-Trp-Ile-Ser-Leu-Ile-Leu-Ser-Leu-Leu-Ala-Leu-Ser-Ser-Gly-Ala-Ile-Ser (19 residues); in MOPC-41 kappa L-chain precursor, Met-Asp-Met-Arg-Ala-Pro-Ala-Gln-Ile-Phe-Gly-Phe-Leu-Leu-Leu-Leu-Phe-Pro-Gly-Thr-Arg-Cys (22 residues). The extra pieces in the precursors of MOPC-104E (lambda1), MOPC-41 (kappa), and MOPC-321 (kappa) L-chains differ extensively from each other in their amino acid sequence (65-73%). In addition to this sequence heterogeneity, the extra pieces are characterized by a high percentage of hydrophobic residues: 69% in the MOPC-104E lambda1 L-chain precursor (this report), 73-75% in the kappa L-chain precursors [Schechter, I. & Burstein, Y. (1976) Proc, Natl. Acad. Sci. USA 73, 3273-3277]. The marked hydrophobicity of the extra piece suggests that it may favor interaction of the precursor with cell membranes, in a manner similar to the function of the "hydrophobic domain" of membrane-bound proteins. We propose two possible targets for interaction: (i) the endoplasmic membranes, where the NH2-terminal extra piece is cleaved from the precursor to yield mature protein destined for secretion; (ii) the cell surface membrane, where the intact precursor is anchored by virtue of the hydrophobic extra piece to serve as the antigen-recognizing receptor.

Amino Acid Sequence↗
PubMed1977

Independent expression of the gene coding for the constant domain of immunoglobulin light chain: evidence from sequence analyses of the precursor of the constant region polypeptide.

The mRNA coding for the kappa-type constant region (C(kappa)) was purified from two clones derived from the MPC-11 mouse myeloma. This mRNA directs the cell-free synthesis of a C(kappa) precursor (molecular weight, about 15,000) in which an extra piece, 17 residues long, precedes the NH(2)-terminal residue (Ala(109)) of the C(kappa) region. The partial sequence of the extra piece is: Met-X-Thr-Asp-Thr-Leu-Leu-Leu-Trp-Val-Leu-Leu-Leu-Trp-Val-Pro-X- (X is unknown). Met(1) was shown to be the initiator methionine. The sequence of the C(kappa) extra piece is completely different from any known sequence preceding residue Ala(109) in whole light (L) chains, thus establishing that the C(kappa)-region mRNA could not have originated from mRNA coding for the whole L chain. The structural features of the C(kappa) extra piece (marked hydrophobicity, size, and a methionine at the NH(2)-terminus) are identical to those characteristic of the NH(2)-terminal extra piece linked to the variable (V) region of whole L-chain precursors. In addition, the C(kappa) extra piece and the extra piece linked to the V region of MOPC-321 L chain have 70% sequence homology. These findings can be explained by the two genes-one Ig chain hypothesis, if we assume that the DNA coding for the extra piece (xp-DNA) is a constitutive part of the V gene. According to this model, the C(kappa)-region mRNA could have originated from: (i) translocation of this V gene to the C gene, deletion of the entire mature V gene, and "end-to-end" repair of the remaining xp-DNA to the C gene; (ii) translocation to the C gene only of the xp-DNA portion of the V gene. Alternatively, we may assume that the xp-DNA is not covalently linked to the mature V gene at all times, as might be the case for the DNA of hypervariable regions presumed to be in episomes. This raises the intriguing speculation that the xp-DNA represents a third distinct gene, designated xp-gene. The presumed xp-gene may be involved in the regulation of gene transcription: when linked to the mature V gene it initiates a chain of events leading to whole L-chain mRNA formation; when attached to the C gene it leads to its transcription to provide the C-region mRNA.

Amino Acid Sequence↗
PubMed1976

Selective chemical cleavage of tryptophanyl peptide bonds by oxidative chlorination with N-chlorosuccinimide.

Tryptophanyl peptide bonds are selectively cleaved by N-chlorosuccinimide (NCS) under acidic conditions. All other peptide bonds are resistant to cleabage by this reagent. Optimal conditions for cleavage are: 2 equiv of NCS, pH 4-5, or 50-80% acetic acid for 30 min at room temperature. Under these conditions methionine residues are oxidized to methionine sulfoxides and cysteine. Other amino acids are not modified. The cleavage reaction was studied with several peptides containing tryptophan residueas successfully applied to several proteins. In alpha-lactalbumin, Kunitz trypsin inhibitor ,and apomyoglobin, selective cleavage of the expected tryptophanyl peptide bonds was obtained in 19-58% yield. The glucagon molecule was fragmented into two peptides in 32% yield.

Amino Acid Sequence↗
PubMed1976

Amino acid-sequence variability at the N-terminal extra piece of mouse immunoglobulin light-chain precursors of the same and different subgroups.

The proteins programmed in the wheat-germ cell-free system by the mRNA coding for the MOPC-63 mouse myeloma L (light) chain were labelled with six radioactive amino acids: [35S]methionine, [4,5-3H]leucine, [3,4-3H]proline, [3-3H]serine, [4,5-3H]isoleucine or [2,3-3H]alanine. Amino acid-sequence analyses showed that over 90% of the total cell-free product was one homogeneous protein, which corresponds to the MOPC-63 L-chain precursor. In this precursor an extra piece, 20 amino acid residues in length, precedes the N-terminus of the mature L chain. The extra piece contains one methionine residue at the N-terminus, six leucine residues, which are clustered in two triplets at positions 6, 7, 8 and 11, 12, 13, one proline residue at position 16, and one serine residue at position 18. The closely gathered leucine residues, as well as their abundance (30%), suggest that the extra-piece moiety is hydrophobic. In the precursors, the extra piece is coupled to the variable region of the L chain. Partial sequences of precursors of L chains of the same and different subgroups that were labelled with the above six radioactive amino acids indicate that the extra piece is part of the variable region. Thus the precursors of MOPC-63 and MOPC-321 L chains, which are of the same subgroup, have extra pieces of identical size (20 residues), and so far their partial sequences are also identical (see above). On the other hand, in the precursor of MOPC-41 L chain, which is of a different subgroup, the extra piece is 22 residues in length. Further, the sequence of the MOPC-41 extra piece differs in at least ten positions from sequences of the extra pieces of the precursors of MOPC-63 and MOPC-321 L chains.

Amino Acid Sequence↗
PubMed1976

Identification of N-terminal methionine in the precursor of immunoglobulin light chain. Initiation of translation of messenger ribonucleic acid in plants and animals.

The proteins programmed in the wheat-germ cell-free system by the mRNA coding for the MOPC-321 mouse myeloma L (light) chain were labelled with [35S]methionine, [4,5-3H]leucine or [3-3H]serine, and were subjected to amino acid-sequence analyses. Over 95% of the total cell-free product was sequenced as one homogeneous protein, which corresponds to the precursor of the L-chain protein. In the precursor, 20 amino acid residues precede the N-terminus of the mature protein. This extra piece contains one methionine residue at the N-terminus, one serine residue at position 18, and six leucine residues, which are clustered in two triplets at positions 6, 7, 8 and 11, 12, 13. The identification of methionine at the N-terminus of the precursor is in agreement with the evidence showing that unblocked methionine is the initiator residue for protein synthesis in eukaryotes. The absence of methionine at position 20, which precedes the N-terminal residue of the mature protein, suggests that myeloma cells synthesize the precursor. However, within the cell the precursor should be rapidly processed to the mature L chain, since precursor molecules have not yet been found in the intact animal. The abundance (30%) of leucine residues indicates that the extra-piece moiety is quite hydrophobic. The extra piece of the MOPC-321 L-chain precursor synthesized with the aid of the Krebs II ascites cell-free system is of identical size and it has the same leucine sequence [Schechter et al. (1975) Science 188, 160-162]. This indicates that cell-free systems derived from the plant and animal kingdom initiate mRNA translation from the same point. It is shown that the amino acid sequence of minute amounts of a highly labelled protein (0.1 pmol) can be faithfully determined in the presence of a large excess (over 2000 000-fold) of unrelated non-radioactive proteins.

Amino Acid Sequence↗
PubMed1976

Partial amino-acid sequence of the precursor of an immunoglobulin light chain containing NH2-terminal pyroglutamic acid.

Analyses of amino-acid sequences of the total cell-free products programmed by the mRNA of MOPC-104E gamma light (L)-chain show that over 95% of the products have sequences of a distinct protein that correspond to the L-chain precursor. In this precursor an extra piece is coupled to the NH2-terminus of the mature L-chain. Analyses of products labeled with [3H]alanine, [3H]leucine, and [3H]proline demonstrate that the extra piece is composed of at least 18 residues. Analyses of [35S]methione-labeled product indicate that the extra piece may contain an additional NH2-terminal methionine, which is detected in about 10% of the molecules. Partial recovery of the NJ2-terminal methionine (alanine, leucine, and proline are recovered in yields close to theoretical, greater than 95%) suggests that it is the initiator methionine, which is known to be short lived in eukaryotes due to rapid hydrolysis. Thus, the extra piece seems to be 19 residues in length, and it contains one methionine at the NH2-terminus, three alanines at positions 2, 12, and 17, and five leucines at positions 6, 8, 10, 11, and 13. The close gathering of leucine residues, as well as their abundance (26%), suggest that the extra piece would be quite hydrophobic. Hydrophobicity seems to be a general property of the extra piece, since similar clusters of leucine were found in the precursors of 3 KL-chains (Burstein, Y. & Schechter, I. (1976) Biochem. J. 157, 145-151). The NH2-terminus of the mature MOPC-104E gamma L-chain is blocked by pyroglutamic acid. The fact that in the precursor a peptide segment precedes this NH2-terminus establishes that pyroglutamic acid is not the initiator residue for synthesis of the L-chain. Apparently, the pyroglutamic acid is formed by cyclization of glutamic acid or glutamine during cleavage of the extra piece to yield the mature L-chain.

Amino Acid Sequence↗
PubMed1976

Marked hydrophobicity of the NH2-terminal extra piece of immunoglobulin light-chain precursors: possible physiological functions of the extra piece.

mRNAs coding for mouse immunoglobulin light chains direct the cell-free synthesis of precursors in which extra peptide segments precede the NH2-termini of the mature proteins. The abundance (18-30%) of leucine residues in the extra piece indicates that it is quite hydrophobic [Schechter and Burstein (1976) Biochem. Biophys, Res. Commun. 68, 489]. Accordingly, we have determined the positions of all hydrophobic residues by sequencing two k-type light (L)-chain precursors that were labeled with: [3H]Ala, [3H]Val, [3H]Leu, [3H]Ile, [3H]Thr, [3H]Pro, [3H]Phe, [3H]Tyr, [3H]Trp, [35S]Met, and [35S]Cys. The partial sequences (and sizes) of the extra pieces obtained are: in MOPC-321 precursor, Met-X-Thr-X-Thr-Leu-Leu-Leu-Trp-Val-Leu-Leu-Leu-Trp-Val-Pro-X-X-Thr-X-(20 residues; X is unknown); in MOPC-41 precursor, Met-X-Met-X-Ala-Pro-Ala-X-Ile-Phe-X-Phe-Leu-Leu-Leu-Leu-Phe-Pro-X-Thr-X-Cys- (22 residues). Despite the fact that these extra pieces differ extensively in sequence (68%), both of them are highly enriched with hydrophobic residues (75% in MOPC-321, 73% in MOPC-41). This marked hydrophobicity suggests that the extra piece favors interaction of the precursor with cell membranes, in a manner similar to the function of the "hydrophobic domain" of membrane-bound proteins (e.g., glycophorin). We propse that the hydrophobic extra piece directs most precursor molecules to the endoplasmic reticulum, where they are cleaved to yield mature L chain destined for scretion; a few precursor molecules escape cleavage and are embedded in the cell surface to serve as the antigen-recognizing receptor. The probability that the Leu-Leu-Leu-Trp-Val sequence occurs by change is 1.6 X 10(-8). Therefore, the data provide evidnece for duplication of a short DNA segment in the structural gene coding for the MOPC-321 precurosr. Duplication with inversion is also indicated from inverted repetition of the Phe-Lue-Leu sequence in the extra piece of the MPOC-41 precursor.

Amino Acid Sequence↗
PubMed1975

Selective oxidation of methionine residues in proteins.

Methionine residues in peptides and proteins were oxidized to methionine sulfoxides by mild oxidizing reagents such as chloramine-T and N-chlorosuccinimide at neutral and slightly alkaline pH. With chloramine-T cysteine was also oxidized to cystine but no other amino acid was modified; with N-chlorosuccinimide tryptophans were oxidized as well. In peptides and denaturated proteins all methionine residues were quantitatively oxidized, while in native proteins only exposed methionine residues could be modified. Extent of oxidation of methionine residues was determined by quantitative modification of the unoxidized methionine residues with cyanogen bromide (while methionine sulfoxide residues remained intact), followed by acid hydrolysis and amino acid analysis. Methionine was determined as homoserine and methionine sulfoxide was reduced back to methionine. Sites of oxidation were identified in a similar way by cleaving the unoxidized methionyl peptide bonds with cyanogen bromide, followed by quantitative end-group analysis of the new amino-terminal amino acids (by an automatic sequencer).

Amino Acid Sequence↗
PubMed1975

Purification of D-alanine carboxypeptidase from Escherichia coli B on a penicillin-Sepharose column.

1. A soluble D-alanine carboxypeptidase from Escherichia coli strain B was purified on a p-aminobenzylpenicillin-Sepharose column. This one-step chromatography followed by an (NH4)2SO4 precipitation yielded an enzyme purified 1200-fold and some of its properties are reported. 2. The pure D-alanine carboxypeptidase was devoid of D-alanine carboxypeptidase II activity and migrated as a single protein band on analytical disc gel electrophoresis. 3. Triton X-100 in the purification procedure is an absolute requirement for obtaining a stable enzyme. 4. The enzymic activity of D-alanine carboxypeptidase was greatly affected in solution of high salt concentrations and varied somewhat with the nature of the cation tested.

Alanine↗
PubMed1975

Evidence of homologous relationship between thermolysin and neutral protease A of Bacillus subtilis.

A comparison of the partial amino-acid sequence of neutral protease A from Bacillus subtilis with the structure of thermolysin (EC 3.4.24.4) from Bacillus thermoproteolyticus reveals that these two proteins are homologous. Of 171 residues placed in neutral protease (54% of the sequence), 83 residues (49%) occur in identical positions in thermolysin, and include nine of the 13 residues previously identified as components of the active site of thermolysin. This similarity provides support for the hypothesis that the two enzymes have similar three-dimensional structures and a common mechanism of action. Since these enzymes differ markedly in their resistance to heat inactivation, a comparison of their structures may eventually provide a chemical basis for explaining the differences in their thermal stability.

Amino Acid Sequence↗
PubMedDate not supplied

GM-CSF induces eosinophilic cell growth-promoting activity on human fetal liver cells.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) has been described as a multi-lineage growth factor that induces in vitro colony formation of bone marrow erythroid burst-forming units (BFU-E), multipotential colony-forming units (CFU-GEMM), granulocyte-macrophage CFU (CFU-GM), granulocyte CFU (CFU-G), macrophage CFU (CFU-M), as well as eosinophil colony-forming units (CFU-Eo). Because of the preeminent role of the liver in fetal hematopoiesis, the effect of human recombinant GM-CSF (hrGM-CSF) on hematopoietic cells isolated from human fetal liver was tested in liquid cultures and in semisolid colony assays. hrGM-CSF induced a significant increase in the number of mature eosinophils in liquid culture and to a lesser extent in semisolid cultures when compared to untreated culture controls. The kinetics of this effect on eosinophils reached its peak on day 21 of culture. When GM-CSF and erythropoietin (Ep) were added simultaneously to the cultures, no significant change in the number of eosinophils compared to hrGM-CSF alone was observed. Ep or granulocyte colony-stimulating factor (G-CSF) did not show any CFU-Eo activity when added separately or simultaneously to both liquid and semisolid cultures. These results indicate that hrGM-CSF alone may be a potent stimulating factor for CFU-Eo obtained from human fetal liver and, in combination with other growth factors, control optimal development of human fetal eosinophils.

Cell Differentiation↗
PubMedDate not supplied

Structure and function of immunoglobulin genes and immunoglobulin precursors.

To gain information on the origin of antibody diversity (somatic mutation or germ line hypothesis) it is necessary to determine the number of V region genes. For this purpose the capacity of a distinct V region probe to hybridize and quantify V genes of the same and different subgroups should be established. Relevant information on this issue was obtained from the extent of cross-hybridization of a distinct L chain cDNA with mRNAs coding for L chains of the same and different subgroups. The results indicated that: (1) V regions of similar amino acid sequence are coded by similar nucleotide sequence (this is not self-evident because of the degeneracy of the genetic code); (2) the nucleic acid probe to one V region may anneal and quantify V genes of members of the same subgroup. Molecular hybridizations of the cDNA probe with nuclear DNA showed that: (1) the number of kappa type C genes is small (about 2 per haploid genome); (2) the number of V genes presumably is also small; (3) there is no amplification of these genes in myeloma cells that produce large amounts of the Ig. These results support the somatic mutation model for the generation of antibody diversity. New information on the structure and controlled expression of Ig genes was obtained from the study of L chain precursors, which are the immediate product of L chain mRNA translation in vitro. In the precursors extra peptide segments (19-22 residues in length) precede the N-terminus of the mature L chain. Amino acid sequence analyses of the precursors provide evidence that: (1) the gene coding for the V region is larger than hitherto known; (2) duplication of a short DNA segment occurred in the structural gene coding for the MOPC-321 precursor; (3) translation of the L chain mRNA may be contingent on the nucleotide sequence coding for the extra piece; (4) cleavage of the extra piece may regulate secretion of mature L chain; (5) the extra piece is remarkably hydrophobic, suggesting that the role of the extra piece is to anchor the precursor in cell membranes, in a manner similar to the function of the "hydrophobic domain" of membrane bound proteins. We propose that most precursor molecules are directed to the endoplasmic reticulum where the extra piece is cleaved to yield mature Ig destined for secretion; a few precursor molecules escape cleavage and are anchored by means of the hydrophobic extra piece in the cell-surface membrane to serve as the antigen-recognizing receptor.

Amino Acid Sequence↗