Pregnancy-associated plasma protein A: purification under mild conditions, peptide mapping and tests for possible interactions with trypsin, plasmin and complement.

Pregnancy-associated plasma protein A (PAPP-A) has been obtained in an enriched state under mild conditions of purification involving cibacron blue dye-ligand chromatography, negative antibody-affinity chromatography and gel filtration. The product was a mixture of PAPP-A and alpha-2-macroglobulin (alpha 2M). The ability of these proteins to bind 125I-trypsin and 125I-plasmin was studied. In contrast to previous studies by others, there was no evidence that PAPP-A could bind either protease. It is pointed out that protease-inhibitory activity in samples of PAPP-A can be due to the presence of very small amounts of contaminating alpha 2M in the preparations of PAPP-A. In further experiments PAPP-A did not inhibit the complement-induced lysis of sensitized red cells. Finally, cyanogen bromide peptide mapping experiments failed to yield evidence of structural homologies between PAPP-A and alpha 2M.

Studies on human pregnancy-associated plasma protein A. Purification by affinity chromatography and structural comparisons with alpha 2-macroglobulin.

Pregnancy-associated plasma protein-A (PAPP-A) has been purified by a combination of methods including antibody-affinity chromatography. The resultant protein, obtained in 16% yield from maternal serum, appeared as a single major component on non-denaturing polyacrylamide and SDS/polyacrylamide gel electrophoresis. The protein showed a single component when analysed by isoelectric focusing under denaturing conditions in the presence and absence of reduction and had a pI of 4.34 and 4.42 respectively. These pI values were indistinguishable from those of alpha 2-macroglobulin (alpha 2M). The molecular weight of the PAPP-A polypeptide as shown by SDS/polyacrylamide-gel electrophoresis was 187000, with a minor component of mol.wt. 82500 that was attributed to proteolysis. Since native PAPP-A had a molecular weight on gel chromatography very similar to that of alpha 2M (620000--820000), it was concluded that PAPP-A was a homotetramer. In the absence of reduction, a high-molecular-weight (420000) protomer of PAPP-A was found. It was deduced that PAPP-A, like alpha 2M, is a dinner, whose protomers are composed of disulphide-linked polypeptide chains. It was found that the molecular weight of the PAPP-A polypeptide exceeded that of alpha 2M by 3.3%, but that the total carbohydrate content of PAPP-A exceeded that of alpha 2M by 10% and that its neutral carbohydrate content exceeded that of alpha 2M by between 7.4 and 9.0%. The significance of the estimated molecular weights of alpha 2M (181000) and its major tryptic fragments is discussed in the light of published values. A tryptic fragment alpha 2M (82500 mol.wt.) was apparently the same size as the major tryptic fragment of PAPP-A.

Evaluation of vocal pitch in male transsexuals.

A 49-year-old male-to-female transsexual was administered voice therapy following surgery. Tape recordings were made of her speech prior to and each week during therapy. Selected sentences from these reocrdings were analyzed. Results indicate that changes in both fundamental frequency and perceptual judgments of femininity were statistically significant and supportive to the client. The voice of the client was still discernible from that of a female speaker, although less so than before therapy. It is suggested that a composite treatment program combined with laryngeal modification through surgical intervention may be necessary.