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I Schechter

Publications and source records attributed to I Schechter.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1977

The effects of message speed on auditory comprehension in patients with cerebral cranial injury.

A brief preliminary report is presented on the effects of varying the speed of a spoken message on the performance of motor tasks by patients with cerebral cranial injury. The token test for aphasia was recorded at three different speech time compression/expansion ratios, then presented under sound field (loudspeaker) conditions to three groups of subjects, one of normal young adults as a control, the second of patients with cerebral cranial injury without evidence of aphasia, and the third containing CCI patients with aphasia. Results are reported for speech speed increases (compression) of 25% and 50% and for a speed decrease (expansion) of 35%.

Aphasia↗
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

Binding of 2,4-dinitrophenyl derivatives by the light chain dimer obtained from immunoglobulin A produced by MOPC-315 mouse myeloma.

The light chains, but not the heavy chains, obtained from immunoglobulin A produced by the MOPC-315 mouse myeloma bind the 2,4-dinitrophenyl (DNP) group. Specific interaction with the DNP group was determined by using several immunoadsorbents, including DNP-L-lysine-Sepharose, and elution of the adsorbed light chain by DNP-glycine. Equilibrium dialysis experiments showed that the M-315 light chain in the form of dimer (45 260 daltons) has two identical and homogeneous binding sited that bind DNP-L-lysine with an intrinsic association constant of 6.3 x 103 M-1. This is the first report, to our knowledge, in which the light chain binding data permit reliable determination of the binding constant and valency of the isolated light chain, and which suggests a predominant role for the light chain in construction of the binding site in the intact immunoglobulin molecule.

Binding Sites↗
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

Partial amino acid sequence of the precursor of immunoglobulin light chain programmed by messenger RNA in vitro.

The five proteins programmed in a cell-free system by a mouse kappa light chain messenger RNA were labeled with [3H]leucine and subjected to amino acid sequence analyses. In all five proteins, 20 amino acid residues precede the amino terminus of the mature protein, indicating that there is one major point for the initiation of messenger RNA translation. The abundance (30 percent) of leucine residues in the extra piece (leucine at positions 6, 7, 8, 11, 12, and 13) indicates that this moiety is hydrophobic. Furthermore, it seems that the precursor may have an additional extra piece at the carboxyl terminus.

Amino Acid Sequence↗
PubMed1975

Prolonged retention of glutaraldehyde-treated skin homografts in humans.

Treatment of cadaver skin homografts in vitro with glutaraldehyde significantly prolonged their average retention time from 10.9 to 21.8 days in 21 patients with burns and/or extensive soft tissue injuries. The glutaraldehyde-treated homografts serve as a useful non-viable wound cover. They remain adherent to the wound bed for prolonged periods and support the formation of granulation tissue favourable for the subsequent acceptance of autografts. Toxic symptoms or allergic reactions were not noticed in any of the recipients. Treatment of the skin with glutaraldehyde is simple to perform, requires minimal laboratory equipment, and is not time consuming.

Aldehydes↗
PubMed1975

Region of immunoglobulin light-chain mRNA transcribed into complementary DNA by RNA-dependent DNA polymerase of avian myeloblastosis virus.

The mRNA coding for a kappa-type immunoglobulin light (L)-chain and its complementary DNA (cDNA) hybridize with a Crt1/2 of 2.6 x 10(-4) moles of ribonucleotide x liter-1 x sec, forming well-matched duplexes (melting temperature Tm equals 89 degrees). The molecular weight of the cDNA is about 280,000 (840 nucleotides) as determined by alkaline sucrose gradient centrifugation and from the extent of protection of the mRNA by the cDNA from ribonuclease digestion. The cDNA anneals with kappa-type mRNAs of the same and different subgroups with comparable Crt1/2 values, but not with a lambda-type mRNA. Thus, one kappa-type cDNA can be used to quantify the mRNAs coding for all kappa-type L-chains. The values of cDNA hybridized at saturation with various kappa-type mRNAs indicate that: (1) the cDNA is complementary to the entire constant region and to about half of the variable (V)-region; (2) V-regions of similar amino-acid sequence are coded by a similar nucleotide sequence; (3) the nucleic acid probe to one V-region may anneal and quantify V-region genes of members of the same subgroup.

Avian Leukosis Virus↗
PubMed1975

Prolonged retention of glutaraldehyde-treated skin allografts and xenografts: immunological and histological studies.

Glutaraldehyde (GA)-treated skin allografts and xenografts (from mice, rats and guinea-pigs) behave in the same way as judged from retention time, gross inspection, microscopic examination, and assays for graft antigenicity. The GA-treated grafts are retained for long periods of time (an increase by more than 6-fold as compared to untreated grafts), they are tightly bound to the recipient, they are initially soft but become progressively stiffer with minimal shrinkage in size, and remain free from infection. The histology shows that the grafts are nonviable and fixed by the GA, they are avascularized but the general structure of the skin (epidermis, adnexa and dermis) is preserved for about 3 months. The antigenicity of the GA-treated grafts is very poor, actually it is undetectable. They do not elicit the formation of cytotoxic antibodies, and animals sensitized by untreated allografts retain the GA-treated allografts similarly to normal unsensitized recipients. The lack of transplantation immunity is also indicated by the fact that GA-treated isografts behave and are rejected similarly to GA-treated allografts and xenografts. Microscopic examination suggests that the mechanism of rejection of GA-treated grafts is similar to that operating in the rejection of an inert foreign body. The marked prlongation in the retention of Ga-treated skin grafts and their properties justify investigations on the applicability of these grafts in clinical practice.

Aldehydes↗
PubMed1975

Prognostic factors in rehabilitation after severe head injury. Assessment six months after trauma.

After initial neurosurgical treatment, 40 patients who regained consciousness 1 to 90 days after major cerebral trauma, were admitted for rehabilitation. Six months after their injury they were assessed in terms of: 1) Locomotor function, 2) Intellectual performance, 3) Communication disorder, and 4) behaviour disturbances. The usefulness of these parameters as prognostic factors in rehabilitation is discussed. Eight patients without significant disabilities in all 4 parameters returned to normal life. Patients who showed locomotor, communicative and behaviour impairment but no gross intellectual deficits, were considered capable of being retrained. The poorest prospects for social and vocational rehabilitation were found in 15 patients with cognitive defects.

Adult↗