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H A McKenzie

Publications and source records attributed to H A McKenzie.

At least 19 recordsLinked to original sources
PubMed2001

Apparently anomalous sedimentation behavior in mixed solvent systems with strong interactions between solution components: analysis of nonideal behavior by bovine serum albumin in 7 M urea at pH 3.3.

The use of the analytical ultracentrifuge to study nonideal behavior of macromolecules in multicomponent systems is discussed, noting the value of interference optics to extend the range of concentrations of macromolecule that may be studied. The choice of appropriate theory in the treatment of experimental data is examined, using a study of bovine serum albumin (BSA) in 7 M urea at pH 3.3 as an example. Under these conditions BSA undergoes extensive unfolding and exhibits marked nonideality, with the binding of approximately 200 molecules of urea per molecule of BSA.

Animals↗
PubMed1996

alpha-Lactalbumins and lysozymes.

Lysozyme is ubiquitous in a variety of tissues and secretions. Chick-type (c-type) lysozymes lyse the cell walls of certain bacteria. In contrast, alpha-lactalbumin appears to occur only in mammalian milk and colostrum. It has the unusual property of acting as a modifier protein to modify the action of galactosyl transferase to a lactose synthase. Both proteins have diverged from a common ancestor. This is reflected in the striking relationship between their amino acid sequences, and the high conservation of disulfide bridges, their intron-exon organization, and three-dimensional structures. In studying their evolutionary relationships some important differences are noted, e.g., all alpha-lactalbumins strongly bind Ca(II), but only some c-type lysozymes do so. These properties point the way to future investigations that are necessary before firm conclusions can be made about their evolutionary history.

Animals↗
PubMed1995

Application of high-performance liquid chromatography to determination of modifier activity in alpha-lactalbumin and other proteins.

High-performance liquid chromatography has been applied to determination of modifier activity in alpha-lactalbumin (alpha-LA). An amino-bonded column separates uridine diphosphate (UDP) (product), UDPgalactose (substrate), and uridine monophosphate (UMP). From an aliquot of the same sample, a column for carbohydrate analysis separates lactose (the other product) and galactose-1,2-cyclic phosphate (Gal-c-P). Nucleotide peaks are detected by measurement of A262 and those of carbohydrate by 3H counting, the isotope originating from UDP-galactose-3H. A pH of 6.3 was taken as optimal for production of UDP since, at this level, the unwanted side reaction is minimized, by which UMP and Gal-c-P are formed. Thus, the conservation of substrate so effected may have contributed to an enhanced production of UDP. The reaction by which UDP and lactose are produced was linear for 120 min, as followed by UDP formation, but it continued to at least 300 min. Production of lactose was equivalent to that of UDP, when alpha-LA was the modifying protein. From a survey of seven other proteins, only lysozyme and ovalbumin showed ability to produce UDP. However, failure of the last two proteins to produce lactose indicates absence of modifier activity and demonstrates the need for monitoring both products.

Animals↗
PubMed1994

Models of the three-dimensional structures of echidna, horse, and pigeon lysozymes: calcium-binding lysozymes and their relationship with alpha-lactalbumins.

Similarities in amino acid sequences, three-dimensional structures, and the exon-intron patterns of their genes have indicated that c-type lysozymes and alpha-lactalbumins are homologous proteins, i.e., descended by divergent evolution from a common ancestor. Like the alpha-lactalbumins, echidna milk, horse milk, and pigeon eggwhite lysozymes all bind Ca(II). Models of their three-dimensional structures, based on their amino acid sequences and the known crystal structures of domestic hen eggwhite and human lysozymes and baboon and human alpha-lactalbumins, have been built. The several structures have been compared and their relationships discussed.

Amino Acid Sequence↗
PubMed1993

The isolation and properties of whole casein: some implications for comparative studies.

1. Problems in the isolation of whole casein from bovine milk are considered. A summary is given of our experiences in its isolation. 2. The physical characteristics, sedimentation velocity, heterogeneity, absorptivity, nitrogen, phosphorus and carbohydrate contents of whole casein prepared from normal and sub-clinical mastitic milk samples by a variety of methods are compared. The methods are acid precipitation, high-speed centrifugation, with and without added calcium (II), and ammonium sulphate precipitation. 3. A description is given of the low temperature ammonium sulphate procedure preferred for the isolation of whole casein, especially when it is to be used for subsequent fractionation for conformation and micelle studies. 4. The question of the use of bovine casein as a paradigm for the caseins of other mammalian species and the need for further studies of the physical, chemical and biological properties of the caseins are discussed.

Absorption↗
PubMed1991

Some monotreme milk "whey" and blood proteins.

1. Electrophoretic studies are made of mature phase milk "whey" proteins and blood serum proteins of echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus). The echidna milk bands are designated A-M, those of platypus A-G. Some of the proteins are isolated and characterized. 2. Echidna band A protein has some similarity to high cystine "whey" proteins. Band E protein (apparent Mr 21,000) may be a beta-lactoglobulin-like protein. Band M is lysozyme. Band C is serum albumin. Bands G-K are transferrins. 3. Platypus milk bands A, C, D, F and G are isolated. Bands F and G are transferrins. 4. Lactose synthase and lytic activities are examined.

Amino Acid Sequence↗
PubMed1991

The isolation and amino acid sequences of echidna (Tachyglossus aculeatus) milk lysozyme I and II.

Comparative studies of monotreme proteins are of particular value in gaining an understanding of the origin of mammals and their interrelationships. The presence of two lysozyme variants, echidna lysozyme I and II, has been confirmed in mature milk samples of Tachyglossus aculeatus multiaculeatus and Tachyglossus aculeatus aculeatus respectively. A simplified procedure is described for their isolation. Their amino acid sequences, the first determined for a monotreme secretory protein, are unusual. They are shown to be c-type lysozymes, each consisting of a single chain of 125 residues (terminating at Cys 125). The only other known c-type lysozyme with this termination is that of pigeon eggwhite. Echidna lysozyme is unique in having no Cys at position 6, but at position 9. It has precisely the residues relevant to the binding of Ca(II), and most of the residues implicated in the galactosyl transferase modifier action of alpha-lactalbumin. However, the weak modifier action previously observed for variant I, prepared by a different method, was not found for the present preparation. The evolutionary significance of the results is discussed.

Amino Acid Sequence↗
PubMed1990

Feline whey proteins: identification, isolation and initial characterization of alpha-lactalbumin, beta-lactoglobulin and lysozyme.

1. Both alpha-lactalbumin and beta-lactoglobulin-like proteins were detected in the whey fraction of feline milk by immunoblotting with rabbit antisera to alpha-lactalbumin and beta-lactoglobulin, respectively. 2. alpha-Lactalbumin was found to occur in both glycosylated and unglycosylated forms in approximately equal concentrations. No polymorphism of feline alpha-lactalbumin was found. 3. Feline beta-lactoglobulin-like proteins produced complex electrophoretic patterns that appear to be determined by three distinct loci. Between two and five genetic variants are expressed by each locus. 4. Lysozyme was detected at levels of approximately 1 mg/ml in skim milk. 5. The identifications of the proteins as alpha-lactalbumin, beta-lactoglobulin and lysozyme were confirmed by determination of N-terminal amino acid sequences.

Amino Acid Sequence↗
PubMed1990

Haemoglobin, serum albumin and transferrin variants of Bali (Banteng) cattle, Bos (Bibos) javanicus.

1. Individual blood samples from 144 Bali (Banteng) cattle [Bos (Bibos) javanicus] in the Northern Territory of Australia and from 61 Bali cross cattle, were examined by zone electrophoresis to determine the variants of haemoglobin, serum albumin and transferrin that are present. 2. Of the common cattle haemoglobin variants (A and B) only variant B occurs in the Bali cattle samples. A second variant, designated CBali, occurs in Bali cattle either as the heterozygote (B CBali) or as the homozygote, the frequencies of occurrence indicating a two-allele system of inheritance without dominance. The CBali cross samples may exhibit the homozygous or heterozygous A variant. 3. The CBali variant has an electrophoretic mobility intermediate between those of the A and B variants at pH 8.6 and 9.1 but closer to B than to A (B greater than C greater than A). It appears to be similar in mobility to the C variants found in Indian Khillan (CKhillan) by Naik, Sukumaran and Sanghvi (Anim. Prodn, 1965 I, 275-277), and in Asian cattle by Oishi, Abe and Namikama (Immunogenet. Lett., 1968 5, 170-173) and Abe, Mogi, Oishi, Tanaka and Suzuki (Proc. XIIth Europ. Conf. Anim. Blood Groups Biochem. Polymorphisms 1972, pp. 225-228), but appreciably different from those in Kenyan and Rhodesian cattle (CRhodesia) found by Braend (Anim. Blood Grps Biochem. Genet., 1971 2, 15-21) and Carr (Rhod. J. agric. Res., 1964 3, 62-62A), respectively. It is also different in mobility from the C variant found by Winter, Mayr, Schleger, Dworak, Krutzler and Burger (Res. vet. Sci., 1984 36, 276-283) in the mithun.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Iron(III) binding proteins of echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus).

Iron (III) binding proteins are isolated from echidna (Tachyglossus aculeatus multiaculeatus) and platypus (Ornithorhynchus anatinus) milk and blood. On the basis of several criteria it is shown that the milk proteins are not lactoferrins, but are transferrins similar to the corresponding transferrins from the blood. The heterogeneity of the proteins, particularly the echidna milk transferrin, is, at least in part, due to different levels of sialic acid. Their N-terminal sequences (30 residues) are determined and compared with those of other transferrins and lactoferrins. The role of the proteins is discussed.

Amino Acid Sequence↗
PubMed1990

Sequence studies of rabbit serum transferrin.

Large fragments of rabbit serum transferrin have been prepared by enzymatic digestion with subtilisin and by chemical cleavage with BNPS-skatole. Sequence determinations on fragments from the N-terminal lobe lead to the assignment of 273 residues and those from the C-terminal lobe 267 residues. Together with previous determinations, a total of 614 of the ca 679 residues in rabbit transferrin have been assigned. A number of corrections are made to the preliminary sequence assignments of O.U. Beg, H.A. McKenzie and D.C. Shaw (1988) Biochemistry International 17, 1135-1142.

Amino Acid Sequence↗
PubMed1988

Studies of rabbit serum transferrin.

Rabbit serum transferrin is isolated by a procedure designed to preserve its conformation and disulfide linkages. A progress report is presented on the determination of its amino acid sequence, as part of studies on its primary, secondary and tertiary structure. The sequence of 378 residues, of the approximately 680 residues in the molecule, are determined. Observations are made on the site of carbohydrate attachment, iron binding sites and half-cystine residue location. The results are discussed in relation to the X-ray crystallographic studies of human lactoferrin (lactotransferrin) and of rabbit serum transferrin being made in other laboratories.

Amino Acid Sequence↗
PubMed1988

Studies on a partially purified bovine milk lysozyme.

Bovine milk lysozyme has been partially purified by a method developed in this laboratory. We have shown, by preliminary sequential analysis, and by gel filtration on HPLC, that the product is a mixture of two components. One of these, the enzymically active one, differs in its N-terminal sequence from that of "lysozyme 2", a bovine stomach mucosal enzyme, by 7 residues within the first 39 residues. However, some of its properties differ markedly from those of lysozyme 2. The other component, comprising 70% by weight of the total mixture, bears no sequential resemblance to any protein known to us. Our two component system appears to be the same as the preparation of Chandan et al. (Biochim. Biophys. Acta 110, 289 (1965], which they concluded was an homogeneous preparation of lysozyme.

Amino Acid Sequence↗
PubMed1987

Studies on a trace cell lytic activity associated with alpha-lactalbumin.

alpha-Lactalbumin (alpha-LA) has been examined with a new and sensitive method for determination of lysozyme activity. Samples of bovine, human, equine, and rat alpha-LA exhibited cell lytic activity, from 2 X 10(-6) to 45 X 10(-6) of the specific activity of hen eggwhite lysozyme. The activity was chromatographically inseparable from bovine and human alpha-LA. Bovine serum albumin and purified beta-lactoglobulin were inactive. The pH profiles and reaction kinetics of bovine and human alpha-LA showed differences from those of the corresponding milk lysozymes, indicating that their lytic activities were not likely to have resulted from trace lysozyme content. Thus, it appears that a weak cell lytic activity is inherent to alpha-LA.

Animals↗
PubMed1986

Determination of lysozyme activity at low levels with emphasis on the milk enzyme.

A method is described for the determination of lysozyme (muramidase) activity, whereby sensitivity is maximized by incubation of the reaction mixture (sample, buffer, and substrate (Micrococcus luteus] over an extended period. This approach is made feasible by exploiting our observation that the lytic reaction follows simple kinetic order during this time (e.g., 700 min for bovine lysozyme and 960 min for the eggwhite enzyme at low concentrations). After this period, the reaction rates diminish, indicating biphasic behavior, and eventually become negligible. The kinetic order may vary with both the type of lysozyme and the buffer system used. The limit of detection for bovine milk lysozyme is 100 pg/ml reaction mixture, equivalent to 6 ng/ml milk, for a 50-microliters sample (with reference to hen eggwhite lysozyme). With these limits, the method has proven valuable in our comparative studies, particularly for low levels of activity in bovine milk, but also in secretions and tissue extracts from various other eutherian, metatherian, and prototherian mammals. The method may also be applied to investigation of structure and function in modified forms of the enzyme.

Animals↗
PubMed1985

Studies on equine transferrin--I. The isolation and partial characterization of the D and R variants.

Each of two genetic variants of equine transferrin, D and R, is isolated from the blood of the heterozygote by a gentle fractionation procedure at pH 7.2. It is shown by step gradient polyacrylamide gel electrophoresis at pH 7.9 that each of these phenotypes exhibits two major bands (designated F, fast, and S, slow) and several minor bands. Components corresponding to these bands are separated by ion-exchange chromatography at pH 6.6 and 6.9 respectively for the D and R variants. The F and S components of each variant contain respectively four and two sialic acid residues. The nature of their heterogeneity is, at least in part, due to their varying sialic acid contents. It has not been possible to desialylate them completely by neuraminidase. On the basis of comparative studies of the tryptic and chymotryptic peptide maps of transferrins D and R it is concluded that there are at least two amino acid substitutions--D:R:Asp:Gly and Glu:Gly. These two substitutions are qualitatively in accordance with the difference in the electrophoretic mobility between the two variants at alkaline pH.

Amino Acid Sequence↗
PubMed1985

The amino acid sequence of equine milk lysozyme.

The amino acid sequence of equine milk lysozyme has been elucidated. The study involves the determination of the sequence of the N-terminal region of the whole protein, cyanogen bromide fragments, tryptic and chymotryptic peptides and fragments produced by chemical cleavage after tryptophan residues. The protein consists of a single chain of 129 amino acid residues and has a Mr of 14647. While equine milk lysozyme has the essential features of a c(chick)-type lysozyme, there is only 51% sequence homology with human milk lysozyme and 50% with domestic hen egg white lysozyme. Some of the implications of the large number of differences are discussed.

Amino Acid Sequence↗