Frequencies of plasma protease inhibitor alleles in Australian horse breeds and the recognition of two new alleles

ISO-DALT characterization of 12 'new' equine plasma protease inhibitor (Pi) alleles

Twelve equine protease inhibitory alleles, PiE, H, J, K, L2, O, P, Q, R, V, X, Z, have been characterized in terms of isoelectric point, molecular mass and inhibitory activity to bovine trypsin and chymotrypsin by ISO-DALT electrophoresis. Protein maps for 20 Pi alleles including those of the eight 'Thoroughbred' alleles (PiF, G, I, L, N, S1, S2, U) have now been determined. Five pairs of alleles, S1/S2, G/K, L/L2, P/R and U/Z, possessed varying numbers of common proteins ranging from one protein in the case of G/K and L/L2 to six in the case of U/Z. Based on these results and studies of the abnormal expressions of PiF, PiL and PiS1, a theory of at least three closely linked loci has been postulated to account for the marked heterogeneity of the equine protease inhibitory system.

Subdivision of equine Tf into H1 and H2

Subdivision of equine TfH into two variants, designated H1 (faster) and H2 (slower), has been accomplished by high voltage, thin layer polyacrylamide gel electrophoresis at pH 7.9. Transferrin H1 and H2 have been shown to be controlled by codominant alleles and gene frequencies of the Tf alleles have been determined in the Australian Thoroughbred, Standardbred. Quarter Horse and Arabian Horse breeds.

The effectiveness of using co-dominant polymorphic allelic series for (1) checking pedigrees and (2) distinguishing full-sib pair members

Formulae express the effectiveness of parentage exclusion tests and differences separating full-sib pairs by compounding genotypic information on discrete examples of co-dominant alleles segregating at gene loci on different autosomes. Such polymorphisms occur among structural genes and polymorphic DNA sequences. Two general formulae state the theoretical effectiveness of using co-dominant alleles for (1) testing parentage and (2) distinguishing sibs. The formula for parentage exclusion tates the probability (PE) that a given series of co-dominant alleles of known frequency should detect a falsely recorded father (or mother). The other formula describes how genetic polymorphism can distinguished closely related individuals. It states the probability (PS) that alleles distinguish the members of full-sib pairs, dizygotic twins and tissue chimeras. To derive the two general formulae, particular formulae were calculated for n = 2, 3 and 4 co-dominant alleles. By increasing the numbers of alleles, the formulae were seen to contain recurrent patterns which were then expressed in the two general formulae for n alleles. Some examples demonstrate applications of the two formulae in problems concerning parentage and sibship.

Caprine plasma proteinase inhibitors--II. Genetic analysis

1. Analysis of the inheritances of the variants of five caprine plasma proteinase inhibitor systems in families demonstrated a genetic control of codominant alleles at five loci. 2. The PIA, B, C, D and E proteins are controlled by four (PIA1,2,3,4), three (PIB1,4,0), three (PIC2,3,0), five (PID1,2,3,4,0) and two (PIE1,2) alleles respectively. Null alleles were postulated for the PIB, PIC and PID systems. 3. The frequencies of the alleles differed substantially between the Australian and Texan Angoras and Cashmere breeds of goats. 4. The combined exclusion probability for the five PI systems was as high as 0.82 in the Cashmere breed, indicating the potential of the proteinase inhibitor proteins for parentage control purposes.

The equine major plasma serpin multigene family: partial characterization including sequence of the reactive-site regions

The equine Pi system, which is highly polymorphic and was considered to be controlled by a single locus, has been shown to be controlled by four loci (named Spi 1-4). This system is the equine equivalent of the major human plasma serpin (serine protease inhibitor), human alpha 1 PI. Twenty-two haplotypes of the equine Pi system have been characterized by two-dimensional electrophoresis, resulting in the assignment of pI, Mr, and bovine trypsin and chymotrypsin inhibition characteristics to 109 proteins. These proteins have been analyzed further to determine their relatedness to each other as well as to human alpha 1 PI using immunochemical, structural, and functional criteria. The amino acid sequences of the N termini and reactive-site regions have been determined on proteins from each of the four equine Spi loci. This allowed the designation of the proteins from the Spi 1 locus as being METserpins and the functional equivalents of human alpha 1 PI. The Spi 4 proteins are ARGserpins, and by alignment the Spi 2 proteins are ILEserpins, the first so far described. The P1 residue for the Spi 3 proteins was unable to be determined. The limited peptide and immunopeptide mapping revealed that proteins from all four loci were closely related, but within the four there were two pairs (Spi 1 and 2 and Spi 3 and 4) which were more related. All were probably derived from the same gene that gave rise to human alpha 1 PI.

Mammalian alpha 1-antitrypsins: comparative biochemistry and genetics of the major plasma serpin

1. Human alpha 1-antitrypsin (alpha 1 AT) has been extensively characterized and reviewed. It is the archetypal member of the superfamily of serine proteinase inhibitors, the serpins. As human alpha 1-antitrypsin exhibits a relatively high concentration in plasma and is usually the highest concentration serpin, it can be referred to as the major plasma serpin. 2. alpha 1-Antitrypsin from species other than man has been characterized for two major reasons: (1) for use in a model animal system to assist with the study of the human alpha 1 AT deficiency disease; and (2) to find polymorphism for use in gene mapping and linkage studies or for parentage analysis. 3. The diverse range of reasons for studying alpha 1AT has yielded a vast array of literature that is often not well cross-referenced. 4. The characteristic features of alpha 1AT in all species examined to date will be presented with a view to examining which features are important structurally and functionally from an evolutionary perspective. 5. In mouse, horse, rabbit and guinea pig, multigene families which appear to have arisen from alpha 1AT have been found. The functional and evolutionary implications of these paralogous genes will also be discussed.

Equus przewalskii plasma protease inhibitor (Pi) system

A detailed biochemical characterization of four of the five previously described alleles of the plasma protease inhibitor (Pi) system of Equus przewalskii was performed using both one- and two-dimensional electrophoretic techniques. The proteins have been characterized in terms of isoelectric point, relative molecular mass, inhibitory activity to bovine trypsin and chymotrypsin, immunochemical cross-reactivity, terminal sialic acid content and enzyme:inhibitor complex formation and the oxidation sensitivity of this interaction. Using these functional criteria, only three loci (Spi 1, 2 and 3) were found to control the plasma Pi proteins of the E. przewalskii haplotypes. In contrast a fourth locus, Spi 4, was found in some E. caballus haplotypes. The significance of these results with respect to the complexity of the protein pattern exhibited by the equine Pi multigene family is discussed.

Application of an affinity electrophoretic and in situ oxidation method to the study of the equine protease inhibitory proteins

An affinity method was developed to investigate the interaction between protease and protease inhibitor by incorporating a protease incubation step into a two-dimensional electrophoretic separation of the plasma protease inhibitory proteins. This involved the application of the isoelectric focusing gel to filter paper saturated in the protease of choice before being placed on the second-dimensional polyacrylamide electrophoresis gel. General protein staining or immunoblotting was used to detect the protein or ligand in the complex. An in situ oxidation method was developed using the reagent chloramine T to investigate the effect of this reagent on the complexing abilities and inhibitory activities of the protease inhibitory proteins. Oxidation was performed either after electrophoresis prior to staining for enzyme inhibition or during two-dimensional electrophoresis prior to the aforementioned protease incubation. The latter allowed the effect of oxidation on complex formation to be examined. Whole plasmas were utilized as the sources of protease inhibitory proteins with the human and mouse being used as models. The equine protease inhibitory system was examined by the two methods and shown to consist of three classes of inhibitory proteins based on their susceptibilities to oxidation and abilities to form complexes with various proteases.