Evidence of tandem repeat and extra thiol-groups resulted in the polymeric formation of bovine haptoglobin: a unique structure of Hp 2-2 phenotype.
Human plasma Hp is classified as 1-1, 2-1, and 2-2. They are inherited from two alleles Hp 1 and Hp 2, but there is only Hp 1 in almost all the animal species. Hp 2-2 molecule is extremely large and heterogeneous associated with the development of inflammatory-related diseases. In this study, we expressed entire bovine Hp in E. coli as a alphabeta linear form. Interestingly, the antibodies prepared against this form could recognize the subunit of native Hp. In stead of a complicated column method, the antibody was able to isolate bovine Hp via immunoaffinity and gel-filtration columns. The isolated Hp is polymeric containing two major molecular forms (660 and 730 kDa). Their size and hemoglobin binding complex are significantly larger than that of human Hp 2-2. The amino-acid sequence deducted from the nucleotide sequence is similar to human Hp 2 containing a tandem repeat over the alpha chain. Thus, the Hp 2 allele is not unique in human. We also found that there is one additional -SH group (Cys-97) in bovine alpha chain with a total of 8 -SH groups, which may be responsible for the overall polymeric structure that is markedly different from human Hp 2-2. The significance of the finding and its relationship to structural evolution are also discussed.
Research Institute of Biochemical Engineering, Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, ROC.
Yi An
YA
Lai
I Hsiang
IH
Lai
Chi Feng
CF
Tseng
James
J
Lee
Simon J T
SJ
Mao
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001483:Base Sequence; D001704:Biopolymers / Q000737:chemistry / Q000235:genetics; D002417:Cattle; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D006242:Haptoglobins / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010641:Phenotype; D020836:Protein Structure, Quaternary; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry; D020080:Tandem Repeat Sequences
D000906:Antibodies; D001704:Biopolymers; D017931:DNA Primers; D006242:Haptoglobins; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds