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PubMed2006

Molecular genetic analysis of 400-year-old human remains found in two Yakut burial sites.

The excavation of five frozen graves at the Sytygane Syhe and Istekh-Myrane burial sites (dated at 400 years old) in central Yakutia revealed five human skeletons belonging to the Yakut population. To investigate the origin and evolution of the Yakut population as well as the kinship system between individuals buried in these two sites, DNA was extracted from bone samples and analyzed by autosomal short tandem repeats (STRs) and by sequencing hypervariable region I (HV1) of the mitochondrial DNA (mtDNA) control region. The results showed a diversity of sepulchral organizations linked probably to the social or genetic background of the subjects. Comparison of STR profiles, mitochondrial haplotypes, and haplogroups with data from Eurasian populations indicated affinities with Asian populations and suggested a relative specificity and continuity of part of the Yakut mitochondrial gene pool during the last five centuries. Moreover, our results did not support a Central Asian (with the exception of maternal lineage of West Eurasian origin) or Siberian origin of the maternal lineages of these ancient Yakut subjects, implying an ethnogenesis of the Yakut population probably more complex than previously proposed.

Biological Evolution↗
PubMed2005

Ancient DNA analysis of human neolithic remains found in northeastern Siberia.

We successfully extracted DNA from a bone sample of a Neolithic skeleton (dated 3,600 +/- 60 years BP) excavated in northeastern Yakutia (east Siberia). Ancient DNA was analyzed by autosomal STRs (short tandem repeats) and by sequencing of the hypervariable region I (HV1) of the mitochondrial DNA (mtDNA) control region. The STR profile, the mitochondrial haplotype, and the haplogroup determined were compared with those of modern Eurasian and Native American populations. The results showed the affinity of this ancient skeleton with both east Siberian/Asian and Native American populations.

Base Sequence↗
PubMed2006

Insights into the "isolation" of the Basques: mtDNA lineages from the historical site of Aldaieta (6th-7th centuries AD).

We analyzed the hypervariable region I (HVR-I) sequence variability of the mitochondrial DNA (mtDNA) of individuals buried at Aldaieta (6th-7th centuries AD) in order to find out more about the biosocial implications of this cemetery. The results, fully authenticated by means of diverse criteria (analysis of duplicates, replication in an independent laboratory, quantification of target DNA, and sequencing and cloning of polymerase chain reaction products), suggest that Aldaieta largely consists of autochthonous individuals who shared common funereal customs with the late Ancient North Pyrenean cemeteries of Western Europe (the Reihengräberfelder), a cultural influence possibly accompanied by a certain genetic flow. Furthermore, the distribution of mtDNA lineages in the cemetery highlighted the existence of a significant number of family relationships, supporting the belief that it was a stable settlement and not a group that had haphazardly settled in the area. Finally, this paper stresses the importance of ancient DNA data for reconstructing the biological history of human populations, rendering it possible to verify certain hypotheses based solely on current population data. The presence at Aldaieta of an mtDNA lineage originating in Northwest Africa testifies to the existence of contact between the Iberian Peninsula and Northwest Africa prior to the Moorish occupation. Both this latter discovery and the high frequency of haplogroup J at the Aldaieta cemetery raise questions about the generally accepted belief that, since ancient times, the influence of other human groups has been very scarce in the Basque Country.

Base Sequence↗
PubMed2006

Population origins in Mongolia: genetic structure analysis of ancient and modern DNA.

In the present study, nuclear (autosomal and Y-chromosome short tandem repeats) and mitochondrial (hypervariable region I) ancient DNA data previously obtained from a 2,300-year-old Xiongnu population of the Egyin Gol Valley (south of Lake Baikal in northern Mongolia) (Keyser-Tracqui et al. 2003 Am. J. Hum. Genet. 73:247-260) were compared with data from two contemporary Mongolian populations: one from the same location (Egyin Gol Valley plus a perimeter of less than 100 km around the valley), and one from the whole of Mongolia. The principal objective of this comparative analysis was to assess the likelihood that genetic continuity exists between ancient and present-day Mongolian populations. Since the ancient Xiongnu sample might have been composed of some of the ancestors of the present-day Yakuts, data from a present-day Yakut population, as well as published data from Turkish populations, were also included in the comparative analysis. The main result of our study was the genetic similarity observed among Mongolian samples from different periods and geographic areas. This result supports the hypothesis that the succession over time of different Turkic and Mongolian tribes in the current territory of Mongolia resulted in cultural rather than genetic exchanges. Furthermore, it appears that the Yakuts probably did not find their origin among the Xiongnu tribes, as we previously hypothesized.

Chromosomes, Human, Y↗
PubMed2003

Lack of paternal inheritance of muscle mitochondrial DNA in sporadic mitochondrial myopathies.

In 2002, paternal inheritance of muscle mitochondrial DNA (mtDNA) was reported in a patient with exercise intolerance and a mitochondrial DNA (mtDNA) mutation restricted to skeletal muscle. To evaluate whether paternal inheritance is a common phenomenon, we studied 10 sporadic patients with skeletal muscle-restricted mtDNA mutations: five harbored mtDNA point mutations in protein-coding genes and five had single mtDNA deletions. We performed haplotype analysis and direct sequencing of the hypervariable regions 1 and 2 of the D-loop in muscle and blood from the patients and, when available, in blood from their parents. We did not observe paternal inheritance in any of our patients.

DNA Mutational Analysis↗
PubMed2002

Reshaping the shared epitope hypothesis: HLA-associated risk for rheumatoid arthritis is encoded by amino acid substitutions at positions 67-74 of the HLA-DRB1 molecule.

OBJECTIVE: To further analyze the association of HLA-DRB1 alleles with disease susceptibility in recent-onset rheumatoid arthritis (RA). METHODS: One hundred sixty-seven Caucasian RA patients and 166 healthy controls were typed for HLA-DRB1. RESULTS: The association of susceptibility to RA with the group of alleles encoding the shared epitope susceptibility sequences (SESSs) was confirmed in recent-onset RA. Among non-SESS alleles, DRB1*07, *1201, *1301, and *1501 showed significant protective effects. Even after correction for the influence of SESS alleles, significant independent protective effects of DRB1 alleles were observed. Protective alleles shared a third hypervariable region motif. Independent homozygosity effects were observed both for susceptibility and for protective alleles. CONCLUSION: Nonsusceptibility alleles differ significantly with regard to RA risk. Protective alleles show clear homology at positions 67-74, often encoding isoleucine at position 67 or aspartic acid at position 70. Susceptibility and protective alleles both show homozygosity effects. Based on these results and on data reported in the literature, in order to incorporate the finding of differential risks among nonsusceptibility alleles, we propose to reshape the shared epitope hypothesis as follows: HLA-associated risk for RA is encoded by amino acid substitutions at positions 67-74 of the HLA-DRB1 molecule.

Adolescent↗
PubMed2002

Interaction between heat-shock protein 73 and HLA-DRB1 alleles associated or not with rheumatoid arthritis.

OBJECTIVE: HLA-DRB1 alleles whose third hypervariable region contains a QKRAA/QRRAA/RRRAA motif are associated with rheumatoid arthritis (RA) through unknown mechanisms. We previously demonstrated that the QKRAA motif was also expressed on the Escherichia coli 40-kd heat-shock protein (HSP) DnaJ. The QKRAA motif helps DnaJ bind its partner chaperone, the E coli 70-kd HSP DnaK. Furthermore, we observed that in lymphoblastoid cells, Hsp73, the constitutive 70-kd HSP, associates with HLA-DRB1*0401 (an allele with a QKRAA motif) and targets it to lysosomes. In this study, we sought to classify different HLA-DRB1 alleles according to their ability to bind Hsp73. METHODS: To evaluate how well different HLA-DRB1 alleles could bind Hsp73, we developed a quantitative precipitation assay and a direct binding assay. RESULTS: Quantitative precipitation assay from total cellular proteins and from lysosomal extracts demonstrated that RA-associated HLA-DRB1 alleles bound Hsp73 better than did HLA-DRB1 alleles that were not associated with RA. HLA-DRB1*0401 was the best Hsp73 binder. These findings were confirmed by direct binding assay between purified proteins. CONCLUSION: HLA-DRB1*0401 was the best Hsp73 binder among the 8 different HLA-DRB1 alleles that were tested.

Alleles↗
PubMed2002

Differences in idiopathic inflammatory myopathy phenotypes and genotypes between Mesoamerican Mestizos and North American Caucasians: ethnogeographic influences in the genetics and clinical expression of myositis.

OBJECTIVE: As part of a larger, worldwide study of the ethnogeography of myositis, we evaluated the clinical, serologic, and immunogenetic features of Mestizo (Mexican and Guatemalan) and North American Caucasian patients with idiopathic inflammatory myopathy (IIM). METHODS: Clinical manifestations, autoantibodies, HLA-DRB1 and DQA1 alleles, and immunoglobulin Gm/Km allotypes were compared between 138 Mestizos with IIM and 287 Caucasians with IIM, using the same classification criteria and standardized questionnaires. RESULTS: IIM in Mestizo patients was characterized by a higher proportion of dermatomyositis (69% of adult Mestizos versus 35% of adult Caucasians; P < 0.001) and anti-Mi-2 autoantibodies (30% versus 7% of adults, respectively, and 32% versus 4% of children, respectively; P < 0.01). Genetic risk factors also differed in these populations. Whereas Mestizos had no HLA risk factors for IIM, HLA-DRB1*0301, the linked allele DQA1*0501, and DRB1 alleles sharing the first hypervariable region motif (9)EYSTS(13) were major risk factors in Caucasian patients with IIM. Furthermore, different HLA-DRB1 and DQA1 alleles were associated with anti-Mi-2 autoantibodies (DRB1*04 and DQA1*03 in Mestizos and DRB1*07 and DQA1*02 in Caucasians). Immunoglobulin gamma-chain allotypes Gm(1), Gm(17) (odds ratio for both 11.3, P = 0.008), and Gm(21) (odds ratio 7.3, P = 0.005) and kappa-chain allotype Km(3) (odds ratio 7.3, P = 0.005) were risk factors for IIM in Mestizos; however, no Gm or Km allotypes were risk or protective factors in Caucasians. In addition, Gm and Km phenotypes were unique risk factors (Gm 1,3,17 5,13,21 and Gm 1,17 23 21 and Km 3,3) or protective factors (Km 1,1) for the development of myositis and anti-Mi-2 autoantibodies (Gm 1,2,3,17 23 5,13,21) in adult Mestizos. CONCLUSION: IIM in Mesoamerican Mestizos differs from IIM in North American Caucasians in the frequency of phenotypic features and in the immune-response genes predisposing to and protecting from myositis and anti-Mi-2 autoantibodies at 4 chromosomal loci. These and other data suggest the likelihood that the expression of IIM is modulated by different genes and environmental exposures around the world.

Adult↗
PubMed1991

Sequence of class II major histocompatibility complex genes from MRL mice. Conserved amino acids in the I-E beta chains from autoimmune mice.

Class II major histocompatibility complex molecules are critical in both normal and abnormal immune responses. Both in mice and in humans, these molecules have been implicated in the development of various diseases, including insulin-dependent diabetes mellitus and systemic lupus erythematosus. The MRL/lpr mouse strain spontaneously develops a lupus-like illness with features that include anti-DNA antibodies, glomerulonephritis, and early death. We evaluated the structure of class II molecules from these mice, to investigate for unique sequences that might contribute to autoimmunity. Utilizing the polymerase chain reaction, we sequenced the second exons from the I-A and I-E genes of MRL/lpr and MRL-+/+ mice. We found that at the nucleotide level, there are several changes between MRL class II genes and the previously sequenced "k" haplotype, but at the protein level, they are identical. Furthermore, by comparing the sequences of class II genes from several strains of autoimmune mice, we found that there are conserved amino acids in the third hypervariable region of the I-E beta chain which may be important in the development of autoimmunity.

Amino Acid Sequence↗
PubMed1992

HLA class II sequence polymorphisms and susceptibility to rheumatoid arthritis in Greeks. The HLA-DR beta shared-epitope hypothesis accounts for the disease in only a minority of Greek patients.

OBJECTIVE: In Northern Europeans, rheumatoid arthritis (RA) is strongly associated with a relatively conserved pentapeptide sequence of HLA-DR beta found notably in the HLA-DR4 subtypes Dw4 and Dw14 and in DR1. A previous serologic study of HLA class II polymorphism in a Greek population with RA failed to show significant associations with any antigen. METHODS: We characterized HLA-DRB polymorphisms in Greek patients with RA and in control subjects by restriction fragment length polymorphism analysis. Allelic DRB subtypes were examined by polymerase chain reaction amplification and oligonucleotide hybridization. RESULTS: DNA analysis in the RA patients showed that although individual HLA-DR allelic associations were weak, a relatively conserved HLA-DR beta motif was significantly associated with RA in this population of Greek patients. The third hypervariable region amino acid sequences QRRAA, QKRAA, or RRRAA were found in the HLA-DR beta 1 of 43.5% of the RA patients versus 15.5% of the controls (uncorrected P = 0.00004). CONCLUSION: Sequences shown to influence susceptibility to RA in patients in the UK also play a role in patients in Greece. However, 57% of Greek patients lack the putative HLA-DR beta motif, which suggests that considerable immunogenetic heterogeneity underlies disease susceptibility in this population.

Amino Acid Sequence↗
PubMed1993

HLA-DR4 subtypes in New Zealand Polynesians. Predominance of Dw13 in the healthy population and association of Dw15 with rheumatoid arthritis.

OBJECTIVE: To analyze HLA-DR4 alleles in New Zealand Polynesians with rheumatoid arthritis (RA). METHODS: Thirty Polynesians and 30 Caucasians with RA, as well as 65 Polynesian and 60 Caucasian healthy blood donors, were DR4 subtyped using the polymerase chain reaction and sequence-specific oligonucleotide probes. RESULTS: The frequency of DR4 (DRB1*04) was increased in both Polynesian (P < 0.001) and Caucasian (P < 0.005) RA patients compared with race-matched controls. Dw4 (DRB1*0401) was detected in 15 of 30 Caucasian patients but only 2 of 30 Polynesian patients (P < 0.001). In Polynesians, RA was associated with Dw15 (DRB1*0405), which was present in 11 of 30 patients and 3 of 65 controls (P < 0.001). Dw13 (DRB1*0403) was the most frequent DR4 allele in healthy Polynesians, but was not significantly associated with RA. CONCLUSION: The predominance of the Dw13 subtype in Polynesians may explain in part the low prevalence of RA in this population. The association of Dw15 with RA in Polynesians supports the hypothesis that the third hypervariable region of DR beta determines susceptibility to RA.

Arthritis, Rheumatoid↗
PubMed1993

Generation and molecular analyses of two rheumatoid synovial fluid-derived IgG rheumatoid factors.

OBJECTIVE: To study the Ig genes that encode IgG rheumatoid factor (IgG-RF) from rheumatoid synovial fluid. METHODS: We used rheumatoid synovial fluid B cells to generate IgG-RF-secreting hybridomas. We then characterized their binding properties and determined their nucleotide sequences. RESULTS: Two monospecific IgG-RFs were obtained. Sequence analysis of the RFs revealed a new V lambda gene family (designated V lambda 9) and extensive somatic diversification, including a duplication-insertion of 18 nucleotides (6 amino acid residues) into a hypervariable region. CONCLUSION: The data provide further support for an antigen-driven response in the sustained production of potentially pathogenic IgG-RFs in rheumatoid synovium.

Amino Acid Sequence↗
PubMed1994

HLA-DRB1 alleles in polymyalgia rheumatica, giant cell arteritis, and rheumatoid arthritis.

OBJECTIVE: Immunogenetic analysis has demonstrated that giant cell arteritis (GCA) and rheumatoid arthritis (RA) are associated with 2 different domains of the HLA-DR4 molecule. The present study was undertaken to evaluate whether polymyalgia rheumatica (PMR) immunogenetically resembles GCA or RA and to determine whether expression of HLA-DRB1 alleles can be used to detect heterogeneity among PMR patients. METHODS: Forty-six patients with PMR, 52 with GCA, 122 with seropositive RA, and 72 normal individuals were genotyped for HLA-DRB1 alleles by allele-specific amplification and subsequent oligonucleotide hybridization. RESULTS: The HLA-DRB1*04 allele was the most frequent among PMR patients (67%). While the expression of allelic variants of the HLA-DR4 family was restricted to HLA-DRB1*0401 and *0404/8 in RA patients, all HLA-DRB1*04 alleles, including B1*0402 and B1*0403, were represented in the PMR group. The distribution of HLA-DRB1 alleles among HLA-DRB1*04 negative patients was similar in those with PMR and those with GCA, and could be distinguished from that in RA patients. In particular, HLA-DRB1*01 alleles, which were found in most HLA-DRB1*04 negative RA patients, were underrepresented in patients with PMR and GCA. CONCLUSION: The distribution of HLA-DRB1 alleles in PMR resembles that found in GCA. PMR and GCA share the associated sequence polymorphism encoded by the second hypervariable region (HVR) of the HLA-DRB1 gene. The HLA-DRB1 association of PMR and GCA can be distinguished from that of RA, which is linked to a sequence motif in the third HVR of DRB1 alleles. The differential role of distinct domains on HLA-DR molecules suggests that multiple biologic functions are regulated by these molecules and that they contribute differently to disease mechanisms. The similarities in the distribution of HLA-DRB1 alleles in PMR and GCA indicates that HLA-DRB1 alleles are not predictive for progression of PMR to the vasculitic lesions that are pathognomonic for GCA.

Aged↗
PubMed1994

Genetic typing of patients with inflammatory arthritis at presentation can be used to predict outcome.

OBJECTIVE: To test the hypothesis that genetic characterization of patients at the time they present with inflammatory arthritis can predict subsequent destructive disease. METHODS: We evaluated 177 patients with early arthritis. Patients were serologically tested for rheumatoid factor (RF) and were DNA oligotyped for the presence of conserved base sequences in the third hypervariable region (HVR3) of the DRB1 gene, previously shown to be associated with severe rheumatoid arthritis (RA). Homozygosity in the patient's genotype was confirmed using restriction fragment length polymorphism analysis. The main outcome measure was radiologic erosions at 1 year. RESULTS: At presentation, 120 patients fulfilled the American College of Rheumatology 1987 criteria for RA, 64% of whom possessed the conserved base sequences, compared with 45% of 347 healthy controls (P < 0.001) and with 56% of 57 patients with other inflammatory arthritis (P not significant). Within the RA population, the frequency of Dw4/Dw14 compound heterozygotes was disproportionately increased. The presence of either HVR3 or RF had a relative risk of 13.49 for erosions, with a sensitivity of 95% (specificity 39%); the presence of both HVR3 and RF had a relative risk of 8.13, with a specificity of 88% (sensitivity 53%). All but 1 patient with the Dw4/Dw14 genotype developed erosions within 1 year. CONCLUSION: Knowledge of a patient's HLA-DR type and RF status allows clinically useful prediction of erosive disease; patients possessing Dw4/Dw14 represent a particularly high-risk subgroup.

Alleles↗
PubMed2006

A new classification of HLA-DRB1 alleles differentiates predisposing and protective alleles for rheumatoid arthritis structural severity.

OBJECTIVE: A new classification of HLA-DRB1 alleles supporting the shared epitope hypothesis of rheumatoid arthritis (RA) susceptibility was recently introduced. We investigated the relevance of this classification in terms of the structural severity of RA. METHODS: The study group comprised 144 patients who were included in a prospective longitudinal cohort of French Caucasoid patients with early RA. Progression of the total radiographic damage score (Sharp/van der Heijde method) was used to quantify the structural severity of RA after 4 years of followup. HLA-DRB1 typing and subtyping were performed by polymerase chain reaction, using a panel of sequence-specific oligonucleotide probes. HLA-DRB1 alleles were classified according to the above-mentioned new system. The association between the HLA-DRB1 allele groups (S1, S2, S3P, S3D, and X) and the structural severity of RA was analyzed with nonparametric statistical tests. RESULTS: The presence of S2 alleles (HLA-DRB1*0401 and HLA-DRB1*1303) was associated with severe forms of RA (P = 0.004); a significant dose effect was observed (P = 0.01). The presence of S3D alleles (HLA-DRB1*11001, HLA-DRB1*1104, HLA-DRB1*12, and HLA-DRB1*16) was associated with benign forms of RA (P < 0.0001), and a significant dose effect was observed (P < 0.01). CONCLUSION: The studied classification of HLA-DRB1 alleles is relevant in terms of RA outcomes. Compared with a previously described classification system, this system differentiates predisposing (S2) and protective (S3D) alleles for RA structural severity, which, respectively, correspond to KRRAA and DRRAA amino acid patterns at position 70-74 of the third hypervariable region of the HLA-DRbeta chain.

Alleles↗
PubMed2006

Molecular characterization of rpoB gene mutations in rifampicine-resistant Mycobacterium tuberculosis isolates from tuberculosis patients in Belarus.

The aim of this study was to investigate the frequency, location and type of rpoB mutations in Mycobacterium tuberculosis isolated from patients in Belarus. Tuberculosis cases are increasing every year in Belarus. Moreover, resistance to anti-tuberculosis drugs, especially to rifampicine, has increased. In this study, 44 rifampicine-resistance M. tuberculosis clinical isolates (including multidrug-resistant isolates) were subjected to DNA sequencing analysis of the hypervariable region (hot-spot) of the rpoB gene originating from different geographical regions in Belarus. Sixteen different types of mutations were identified. The most common point mutations were in codons 510 (47.7%), 526 (45.5%), 523 (40.86%) and 531 (29.5%). Eleven isolates (27.7%) carried one mutation and 23 (52%), 7 (16%), 3 (7%) of isolates carried 2, 3 and 4 mutations, respectively. A characteristic, prominent finding of this study was high frequency of multiple mutations in different codons of the rpoB gene (27.7%) and also the detection of unusual types of mutations in the 510 codon, comprising CAG mutations (deletion or changing, to CTG, CAC or CAT). In our study, the change TTG in codon 531 was found in 92% of isolates and the change TGC in 8% of isolates. A TAC change in codon 526 was not found, but the GAC change was found in all isolates. Isolates of M. tuberculosis isolated in Belarus were characterized by the wide spectrum of the important mutations and might belong to the epidemic widespread clones.

Antitubercular Agents↗
PubMed2003

Molecular structure and developmental expression of three muscle-type troponin T genes in zebrafish.

Troponin T (Tnnt), a troponin component, interacts with tropomyosin and is crucial to the regulation of striated muscle contraction. To gain insight into the molecular evolution and developmental regulation of Tnnt gene (Tnnt) in lower vertebrates, zebrafish Tnnt1 (slow Tnnt), Tnnt2 (cardiac Tnnt), and Tnnt3b (fast Tnnt isoform b) were characterized. The polypeptides of zebrafish Tnnt1, Tnnt2, and Tnnt3b were conserved in the central tropomyosin- and C-terminal troponin I-binding domains. However, the N-terminal hypervariable regions were highly extended and rich in glutamic acid in polypeptides of Tnnt1 and Tnnt2, but not Tnnt3b. The Tnnt2 and Tnnt3b contain introns, whereas Tnnt1 is intron-free. During development, large to small, alternatively spliced variants were detected in Tnnt2, but not in Tnnt1 or Tnnt3. Whole-mount in situ hybridization showed zebrafish Tnnt1 and Tnnt2 are activated during early somitogenesis (10 hr postfertilization, hpf) and cardiogenesis (14 hpf), respectively, but Tnnt3b is not activated until middle somitogenesis (18 hpf). Tnnt2 and Tnnt3b expression was cardiac- and fast-muscle specific, but Tnnt1 was expressed in both slow and fast muscles. We propose that three, distinct, muscle-type Tnnt evolved after the divergence of fish and deuterostome invertebrates. In zebrafish, the developmental regulation of Tnnt during somitogenesis and cardiogenesis is more restricted and simpler than in tetrapods. These new findings may provide insight into the developmental regulation and molecular evolution of vertebrate Tnnt.

Alternative Splicing↗
PubMed1976

Location of light chain tyrosine peptides from the combining site of a rabbit anti-p-azobenzoate antibody.

Peptic peptides containing a tyrosyl residue from the binding site of a rabbit anti-p-azobenzoate antibody were isolated by means of the paired-iodination procedure. The peptides were from the light chain, and the tyrosyl residue is 29, 30, 31, 32, 32A, 32B, 33 at position 30 in the sequence -Val-Tyr-Asn-Asx-Lys-Gly-Leu- and thus is in the first hypervariable region. The sequence of the N-terminal 40 residues was determined. The major antibody-site peptide isolated was a diiodotyrosyl (DIT) tetrapeptide representing residues 30-32A; the monoiodotyrosyl (MIT) tetrapeptide was also isolated, but in a smaller yield. By isoelectric focusing, the light chain appeared to be homogeneous. No heterogeneity was apparent in the light chain sequencing until position 32B when, in addition to the phenylthiohydantoin derivative of tyrosine present as the major residue, a significant amount of the phenylthiohydantoin derivative of glycine was obtained. The glycine presumably represents a light chain variant population and explains the source of the other antibody-site peptides isolated, i.e. two pentapeptides, apparently of the sequence Tyr-Asn-Asx-Lys-Gly, isolated as the DIT and MIT derivatives. The tetrapeptides must have been derived from the peptic cleavage between Lys 32A and Tyr 32B in the major light chain variant and the pentapeptides from the peptic cleavage between Gly 32B and Leu 33 in the other variant. It is interesting that position 30 is occupied by a tyrosyl residue in five out of twelve other rabbit antibody light chains of known sequence (Margolies, M.N. et al., Proc. Nat. Acad. Sci. US 1975.72: 2180). One light chain is from another rabbit anti-p-azobenzoate antibody in which Tyr 30 is apparently not important in hapten binding although a tyrosyl at position 96 is clearly involved in hapten binding (Roholt, O.A. et al., J. Immunol. 1973.111:1367). The other four of the five light chains are from anti-pneumococcal polysaccharide antibodies in which the role of this tyrosyl residue is not known.

Amino Acid Sequence↗