Biomaterial Database

Complete structure of a rat RT1 E beta chain: extensive conservation of MHC class II beta chains. 1985

K A Robertson, and W R McMaster

The rat major histocompatibility complex (RT1 complex) encodes two sets of class II molecules, A alpha A beta and E alpha E beta. A cDNA clone encoding a RT1 E beta chain was isolated from a cDNA library prepared from Wistar (RT1 mu) spleen poly(A) RNA by screening with DNA fragments encoding a RT1 A beta chain. The nucleotide sequence of this cDNA insert was determined and was shown to encode a complete RT1 E beta chain. The RT1 E beta chain was highly homologous in terms of sequence identities to H-2 E beta and HLA-DR beta chains. Comparisons of predicted protein sequences of RT1, H-2, and HLA E beta and A beta chains showed that class II beta-chains are highly conserved with 105 out of 278 residues identical in all six beta-chains. The divergences in terms of the number of silent and replacement nucleotide substitutions between class II E beta or A beta sequences showed that the number of replacement substitutions reached a plateau after 10 million yr. Replacement substitutions therefore may be under selective pressure during evolution. The accumulation of silent and replacement substitutions in RT1 and H-2 class II beta-chains was faster than that in HLA beta-chain sequences. Thus, it appears that class II beta chains may be evolving at different rates in different species.

UI	MeSH Term	Description	Entries
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D005075	Biological Evolution	The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.	Evolution, Biological
D005802	Genes, MHC Class II	Genetic loci in the vertebrate major histocompatibility complex that encode polymorphic products which control the immune response to specific antigens. The genes are found in the HLA-D region in humans and include H-2M, I-A, and I-E loci in mice.	Class II Genes,Genes, Class II,Genes, HLA Class II,MHC Class II Genes,Class II Gene,Gene, Class II
D006649	Histocompatibility Antigens	A group of antigens that includes both the major and minor histocompatibility antigens. The former are genetically determined by the major histocompatibility complex. They determine tissue type for transplantation and cause allograft rejections. The latter are systems of allelic alloantigens that can cause weak transplant rejection.	Transplantation Antigens,Antigens, Transplantation,Histocompatibility Antigen,LD Antigens,SD Antigens,Antigen, Histocompatibility,Antigens, Histocompatibility,Antigens, LD,Antigens, SD
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D000949	Histocompatibility Antigens Class II	Large, transmembrane, non-covalently linked glycoproteins (alpha and beta). Both chains can be polymorphic although there is more structural variation in the beta chains. The class II antigens in humans are called HLA-D ANTIGENS and are coded by a gene on chromosome 6. In mice, two genes named IA and IE on chromosome 17 code for the H-2 antigens. The antigens are found on B-lymphocytes, macrophages, epidermal cells, and sperm and are thought to mediate the competence of and cellular cooperation in the immune response. The term IA antigens used to refer only to the proteins encoded by the IA genes in the mouse, but is now used as a generic term for any class II histocompatibility antigen.	Antigens, Immune Response,Class II Antigens,Class II Histocompatibility Antigen,Class II Major Histocompatibility Antigen,Ia Antigens,Ia-Like Antigen,Ia-Like Antigens,Immune Response Antigens,Immune-Associated Antigens,Immune-Response-Associated Antigens,MHC Class II Molecule,MHC II Peptide,Class II Antigen,Class II Histocompatibility Antigens,Class II MHC Proteins,Class II Major Histocompatibility Antigens,Class II Major Histocompatibility Molecules,I-A Antigen,I-A-Antigen,IA Antigen,MHC Class II Molecules,MHC II Peptides,MHC-II Molecules,Antigen, Class II,Antigen, I-A,Antigen, IA,Antigen, Ia-Like,Antigens, Class II,Antigens, Ia,Antigens, Ia-Like,Antigens, Immune-Associated,Antigens, Immune-Response-Associated,I A Antigen,II Peptide, MHC,Ia Like Antigen,Ia Like Antigens,Immune Associated Antigens,Immune Response Associated Antigens,MHC II Molecules,Molecules, MHC-II,Peptide, MHC II,Peptides, MHC II
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D013045	Species Specificity	The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.	Species Specificities,Specificities, Species,Specificity, Species
D014644	Genetic Variation	Genotypic differences observed among individuals in a population.	Genetic Diversity,Variation, Genetic,Diversity, Genetic,Diversities, Genetic,Genetic Diversities,Genetic Variations,Variations, Genetic