The reference OMIM entry for this protein is 120960

Complement component 8, beta subunit; c8b
Complement component c8b
C8 beta

DESCRIPTION

The eighth component of complement (C8) belongs to the late-acting complement proteins (C5-C9) forming the membrane attack complex. C8 is a serum protein that consists of 3 nonidentical subunits arranged asymmetrically as a disulfide-linked alpha-gamma dimer (C8A, 120950; C8G, 120930) and a noncovalently associated beta chain (C8B). Each component is encoded by a different gene (Ng et al., 1987; Kaufmann et al., 1993).

GENE STRUCTURE

Herrmann et al. (1989) estimated the size of the C8B gene to be 32 to 36 kb. By using PCR primers located in the adjacent intron sequences of C8B, Kaufmann et al. (1993) could amplify all 12 exons of the C8B gene from genomic DNA. These analyses and the insert sizes of the genomic lambda clones indicated that the C8B gene has a total size of approximately 40 kb.

MAPPING

The C8A and C8B genes are closely linked on chromosome 1p (Rogde et al., 1986). Bahary et al. (1991) mapped the murine homolog of C8B to chromosome 4.

MOLECULAR GENETICS

By direct sequence analysis of all exon-specific PCR products from normal and C8B-deficient persons, Kaufmann et al. (1993) found a single C-T change in exon 9 leading to a stop codon (R428X; 120960.0001). An allele-specific PCR system was designed to detect the normal and the deficiency allele simultaneously. Using this approach as well as PCR typing of the TaqI polymorphism located in intron 11, 5 families with 7 C8B-deficient members were investigated. The mutant allele was observed in all families investigated and could therefore be regarded as a major cause of C8B deficiency in Caucasians. In 2 C8B-deficient patients, only 1 chromosome carried the C-T change; the molecular nature of the other allele had not been determined. In a study of 34 unrelated families with C8B deficiency from the U.S. and the former U.S.S.R., Saucedo et al. (1995) found that 59 (86%) of 69 null alleles were due to the C-to-T transition in exon 9. An additional 6 null alleles were caused by C-to-T transitions in exons 3 (120960.0003 and 120960.0004) and 6 (120960.0002). Two null alleles were caused by cytosine deletions in exons 3 (120960.0005) and 5 (120960.0006). Of the null alleles, 97% were C-to-T transitions in which an arg (64 alleles) or gln (1 allele) was replaced by a stop codon. - C8B Mutation Nomenclature Using current recommendations for mutation nomenclature, Arnold et al. (2009) numbered nucleotides of the C8B gene starting at the A of the ATG translational start site of the coding reference sequence GENBANK NM_000066. They noted that, traditionally, C8B nucleotides had been numbered starting at the 5-prime end of cDNA clone GENBANK M16973. In their Table 2, Arnold et al. (2009) provided a comparison of the recommended mutation nomenclature used by them with the traditional mutation nomenclature used by others, including Kaufmann et al. (1993), Saucedo et al. (1995), and Rao et al. (2004), along with the corresponding protein changes. ... More on the omim web site

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May 12, 2019: Protein entry updated
Automatic update: model status changed

Nov. 17, 2018: Protein entry updated
Automatic update: model status changed

Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated

Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated

Nov. 23, 2017: Protein entry updated
Automatic update: Uniprot description updated

Oct. 26, 2017: Protein entry updated
Automatic update: model status changed

March 25, 2017: Additional information
No protein expression data in P. Mayeux work for C8B

March 16, 2016: Protein entry updated
Automatic update: OMIM entry 120960 was added.

Jan. 24, 2016: Protein entry updated
Automatic update: model status changed