The isolation and characterization of the soluble and membrane-bound porcine cytochrome b5 cDNAs.

In some male pigs, there is an increased production of the testicular 16 androstene steroids which end up being concentrated in fatty tissue. When the meat is cooked, a disagreeable odor/flavor is produced, a phenomenon known as "boar taint." All boars selected for food production are castrated even though only ca 10% of boars may be "tainted.

The isolation and characterization of the human cytochrome b5 gene.

From a series of lambda and cosmid libraries, we isolated DNA sequences corresponding to the complete coding region for the human cytochrome b5 (CYB5) gene. The overall gene organization was the same as the bovine and rabbit CYB5 genes. One cosmid clone containing exon I plus the 5' flanking region was extensively characterized.

Stopped-flow fluorescence studies of the interaction of a mutant form of cytochrome b5 with lipid vesicles.

Cytochrome b5 binds spontaneously to lipid vescles and also self-associates in aqueous solution. Two mutant proteins have been generated, one has a self-association constant which is less than that of the native protein, while the other has a larger self-association constant. All three proteins have Trp in the membrane-binding domain but as aqueous solutions of these proteins contain differing amounts of monomeric protein, the kinetics of fluorescence enhancement, when the proteins are mixed with lipid vesicles, are complex.

A splicing mutation in the cytochrome b5 gene from a patient with congenital methemoglobinemia and pseudohermaphrodism.

We have analyzed reticulocyte and leukocyte mRNAs isolated from a patient with congenital methemoglobinemia and pseudohermaphrodism. The cytochrome b5 cDNA sequences were amplified using specific oligonucleotide primers and the polymerase chain reaction (PCR). DNA sequencing indicated that there was a 16-bp deletion in the cDNA leading to a new, in-frame stop signal and resulting in a truncated protein of 45 amino acids.

Amino acid substitutions in the membrane-binding domain of cytochrome b5 alter its membrane-binding properties.

The structure-function relationships of the 43-amino-acid membrane-binding domain of cytochrome b5 have been examined in two mutant forms of the protein. In one mutant, two tryptophans in the membrane-binding domain, at positions 108 and 112, were replaced by leucines, and in the second mutant, in addition, aspartic acid 103 was also replaced by leucine. The fluorescence emission spectra of the three proteins and their degree of quenching by brominated lipids indicate that the mutations are not producing major conformational changes or allowing a deeper degree of penetration of the domain into the bilayer.