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Biomedical subjects

Z H Zaidi

Publications and source records attributed to Z H Zaidi.

At least 19 recordsLinked to original sources
PubMed1995

Isolation, characterization and structure of subtilisin from a thermostable Bacillus subtilis isolate.

A serine protease has been isolated and characterized from Bacillus subtilis, strain RT-5 (a thermostable soil isolate from the Tharparkar desert of Pakistan) able to grow at 55 degrees C. The primary structure was established by a combination of protein and DNA-sequence analyses. The amino-acid sequence, inhibition pattern and solubility properties identify the enzyme as a subtilisin. It has 43 amino-acid replacements toward subtilisin BPN' and as much as 83 replacements toward another subtilisin, confirming that strain variabilities are extensive between different subtilisin forms. However, the structure is identical to one of unknown functional properties deduced from DNA and is closely related to mesentericopeptidase but that homologue is not thermostable. From comparisons with that form and with subtilisin BPN', it is concluded that replacements of Ala --> Ser at positions 85 and 89, Ser --> Ala at position 88 and Asp or Ser --> Asn at position 259 may promote thermostability.

Amino Acid Sequence↗
PubMed1995

Oxygen transport proteins: I. Structure and organization of hemocyanin from scorpion (Buthus sindicus).

Scorpions are regarded as the oldest terrestrial arthropods. Scorpion Buthus sindicus (Buthidae) is commonly found in Pakistan and the Mediterranean region. The hemolymph of most arthropods contains large multisubunit, extracellular metalloprotein commonly known as hemocyanin which performs the important function of oxygen transport. The literature available to date shows that no attempt has been made to study hemocyanins or hemolymph proteins from this species. This communication presents the isolation, characterization and partial structural studies on hemocyanin from scorpion Buthus sindicus. (1) The hemolymph was collected by cardiac puncture, centrifuged and subjected to polyacrylamide gel electrophoresis and isoelectric focussing. (2) Crude hemolymph was subjected to gel filtration and high performance ion-exchange chromatography. (3) Purified hemocyanin subunits Bsin 1, 2 and 3 have been analysed for their amino acid composition and N-terminal sequence. The sequence homology was determined by comparison with other arthropod hemocyanin. The results are discussed.

Animals↗
PubMed1994

Three-dimensional model and quaternary structure of the human eye lens protein gamma S-crystallin based on beta- and gamma-crystallin X-ray coordinates and ultracentrifugation.

A 3-dimensional model of the human eye lens protein gamma S-crystallin has been constructed using comparative modeling approaches encoded in the program COMPOSER on the basis of the 3-dimensional structure of gamma-crystallin and beta-crystallin. The model is biased toward the monomeric gamma B-crystallin, which is more similar in sequence. Bovine gamma S-crystallin was shown to be monomeric by analytical ultracentrifugation without any tendency to form assemblies up to concentrations in the millimolar range. The connecting peptide between domains was therefore built assuming an intramolecular association as in the monomeric gamma-crystallins. Because the linker has 1 extra residue compared with gamma B and beta B2, the conformation of the connecting peptide was constructed by using a fragment from a protein database. gamma S-crystallin differs from gamma B-crystallin mainly in the interface region between domains. The charged residues are generally paired, although in a different way from both beta- and gamma-crystallins, and may contribute to the different roles of these proteins in the lens.

Amino Acid Sequence↗
PubMed1994

Primary structure of hemoglobin from cobra Naja naja naja.

Cobra snake Naja naja naja hemoglobin shows four bands on Triton electrophoresis. We present the primary structure of one alpha and one beta chain. The separation of polypeptide chains was achieved by ion exchange chromatography on carboxymethyl cellulose column. The amino acid sequence was established by automatic Edman degradation of the native chains and tryptic and hydrolytic peptides in a gas-phase sequencer. The structural data are compared with those of human and other reptile hemoglobins and reveal not only large variations from human but within reptiles. The amino acid exchanges involve several subunit contacts and heme binding sites. This is the first study on the hemoglobin of a land snake. There are only two amino acid sequences of sea snake hemoglobin (Microcephalophis gracilis gracilis and Liophis miliaris) reported in the literature.

Amino Acid Sequence↗
PubMed1992

Primary structure of beta s-crystallin from human lens.

The complete primary structure of beta s-crystallin from human lens is reported. The sequence was elucidated by automatic Edman degradation of tryptic and CNBr peptides. The blocked N-terminal dipeptide was identified by fast-atom-bombardment mass spectroscopy. The sequence comparison with other members of crystallin family reveals a closer relationship to human gamma-crystallin (53% identity) than with beta A3/A1 crystallin (37% identity). The structure, evolutionary characteristics and role of beta s-crystallin in lens are discussed.

Amino Acid Sequence↗
PubMed1992

Structural characterization of rabbit brain ubiquitin.

Ubiquitin has been isolated and purified from rabbit brain using gel permeation and reverse-phase high-performance liquid chromatography. The 76-residue protein exhibits one difference towards a murine form, is identical to other characterized vertebrate ubiquitins, and confirms an extensive conservation of the ubiquitin structure. No positional microheterogeneities were detectable between two sub-forms.

Amino Acid Sequence↗
PubMed1991

Purification and characterization of two highly different group II phospholipase A2 isozymes from a single viperid (Eristocophis macmahoni) venom.

Two phospholipase A2 isozymes have been purified from leaf-nosed viper by gel permeation chromatography followed by reverse-phase HPLC and cation-exchange FPLC. Both enzymes contain seven pairs of half-cystine, typical of group II phospholipase A2. Surprisingly large differences, affecting both N- and C-terminal regions, exist between the two isozymes purified from the same snake venom. Exchanges occur at no less than 27 of 121 positions (22%), suggesting the possible existence of two genes for phospholipase A2. The residue identity with the enzymes from other Viperidae species is also low, only 44-48%, indicating extensive variations of this protein structure at large. Functionally, the present isozymes do not possess the cationic regions ascribed to myotoxicity and anti-coagulant effects of the enzyme.

Amino Acid Sequence↗
PubMed1991

Extensive multiplicity of the miscellaneous type of neurotoxins from the venom of the cobra Naja naja naja and structural characterization of major components.

A multiplicity of miscellaneous type neurotoxins were detected in the venom of the cobra Naja naja naja by use of reverse-phase HPLC and FPLC. The primary structures of major forms were determined, giving 4 novel structures. All four contain 62-65 residues, with 10 half-cystine residues and resemble the miscellaneous type of toxins from other Naja species. Differences within the species are extensive, exchanges occur at 27 positions, giving only 58% residue identity between all forms. However, the differences are largely limited to 3 regions corresponding to structurally important loops where two functional residues participating in receptor binding are exchanged. The four miscellaneous neurotoxins now characterized, together with the minor components of the miscellaneous type, the minimally four neurotoxins reported before, and other related toxins, indicate the existence of an extensive toxin gene multiplicity.

Amino Acid Sequence↗
PubMed1991

Characterization of phospholipase A2 from the venom of Horned viper (Cerastes cerastes).

Phospholipase A2 has been purified from the venom of Horned viper (Cerastes cerastes) by gel permeation chromatography followed by reverse-phase HPLC. The primary structure was established by sequence analysis of the intact protein and its enzymic peptides. The structure has 120 residues, properties like other group IIB phospholipases, but only 45-55% identity with the enzyme from other viperid species, and large variations even within the species (26% residue differences at known positions in another form).

Amino Acid Sequence↗
PubMed1991

Primary structure of hemoglobin alpha-chain from cuckoo (Eudynamys scolopaceae, cuculiformes).

The complete amino acid sequence of the alpha A-chain of major hemoglobin component from Cuckoo (Eudynamys scolopaceae) is presented. Separation of the polypeptide subunits was achieved by ion exchange chromatography in the presence of 8 M urea. The sequence was studied by automatic Edman degradation of the native chain and its tryptic fragments in a gas-phase sequencer. Comparison with other avian hemoglobins shows residues alpha 21, alpha 30, alpha 96, alpha 110, and alpha 114 as being specific to Cuckoo. The functional significance of these is discussed.

Amino Acid Sequence↗
PubMed1991

Primary structure of hemoglobin beta-chain from Columba livia (gray wild pigeon).

Primary structure of beta-chain of pigeon is presented. It was determined by amino acid sequence analysis of intact beta-chain and its peptides obtained by the enzymatic and chemical cleavage. Comparison of amino acid sequence of the chain with other available data shows beta 14 Ile, beta 61 Lys, and beta 113 Ile as residues specific to pigeon. One important replacement at alpha 1 beta 1 contact is beta 55 Met----Ser.

Amino Acid Sequence↗
PubMed1990

Primary structure and functional properties of cobra (Naja naja naja) venom Kunitz-type trypsin inhibitor.

A trypsin inhibitor from the venom of the cobra Naja naja naja has been isolated by a single step of reverse-phase high-performance liquid chromatography. The protein strongly inhibits trypsin (Ki = 3.5 pM). The primary structure was determined by peptide analysis of the [14C]carboxymethylated inhibitor. The 57-residue polypeptide chain belongs to the family of Kunitz-type inhibitors, and exhibits 42% residue identity with bovine pancreatic trypsin inhibitor. The structure shows only 70% identity with the corresponding peptide from the Capa cobra (Naja nevia), establishing that the inhibitor molecule exhibits extensive variations. Functionally, a basic residue at position P3' correlates with strong inhibition.

Amino Acid Sequence↗
PubMed1990

Purification and characterization of a chymotrypsin Kunitz inhibitor type of polypeptide from the venom of cobra (Naja naja naja).

A chymotrypsin Kunitz inhibitor type of polypeptide has been isolated from the venom of Naja naja naja by reverse phase HPLC and cation exchange FPLC. It is present in a considerably lower amount than that of the corresponding trypsin inhibitor. The primary structure, determined by sequence analysis of the whole molecule and its tryptic peptides, has 57 residues with an apparent molecular mass of 6.2 kDa. The main contact site with the protease (P1) has a Phe, showing the specificity of the inhibitor. Of residues considered functionally important in Kunitz-type inhibitors, Gly-36 is replaced by Ser in a segment of weak contacts with the protease.

Amino Acid Sequence↗
PubMed1990

Characterization of a cytotoxin-like basic protein from the cobra (Naja naja naja) venom.

A cytotoxin-like basic protein has been isolated from the venom of the nominate race of cobra (Naja naja naja from Pakistan) by a single step of high-performance liquid chromatography. The primary structure was determined and consists of 62 amino acid residues in a single polypeptide chain. It is highly similar to that of the cytotoxin-like basic proteins isolated from other Naja species, but differs in two of the SS-loop structures from that of cytotoxins.

Amino Acid Sequence↗
PubMed1990

Sea snake (Microcephalophis gracilis) hemoglobin: primary structure and relationships to other forms.

The hemoglobin of the sea snake Microcephalophis gracilis was purified and the primary structure of the alpha and beta chains determined. This is the first sea snake hemoglobin structure characterized, and apparently also the first complete structure of any snake hemoglobin (an alpha chain of a viper was known), allowing judgments of reptilian variants. Variations between the sea snake form and other reptilian forms are large (52-65 differences for the alpha chains), of similar order as those between the sea snake and avian (56-65 differences) or human (58 differences) forms. Functionally, 19 residues at alpha/beta contact areas and 7 at heme contacts are exchanged in relation to the human alpha and beta chains. Four positions of the sea snake hemoglobin contain residues thus far unique to this form. However, all replacements appear compatible with conserved overall functional properties.

Amino Acid Sequence↗
PubMed1989

Characterization of two different peptides from the venom of the scorpion Buthus sindicus.

Two disulfide-rich, low-molecular mass peptides (approximately 3 kDa and approximately 4 kDa) have been isolated from Buthus sindicus venom using ion-exchange and reverse-phase HPLC. Peptide I has 35 residues with 8 half-cystine residues and is clearly related to four-disulfide core proteins of the neurophysin type and to toxins of other scorpion species (55-63% residue identity). Peptide II, present in low yield, has 28 residues with 6 half-cystine residues and a structure largely dissimilar from that of peptide I and other characterized toxins, although probably still a member of the disulfide core peptide type. Consequently, scorpion venom contains, in addition to toxins characterized before, toxin-like compounds with distant relationships.

Amino Acid Sequence↗
PubMed1989

Primary structure of hemoglobin alpha-chain of Columba livia (gray wild pigeon).

Primary structure of hemoglobin of alpha-chain of Columba livia is presented. The separation of alpha-chain was obtained from globin by ion-exchange chromatography (CMC-52) and reversed-phase HPLC (RP-2 column). Amino acid sequence of intact as well as tryptic digested chain was determined on gas-phase sequencer. Structure is aligned homologously with 21 other species. Among different exchanges, positions alpha 24 (Tyr----Leu), alpha 26 (Ala----Gly), alpha 32 (Met----Leu), alpha 64 (Asp----Glu), alpha 113 (Leu----Phe), and alpha 129 (Leu----Val) are unique to pigeon hemoglobin. The various exchanges in alpha-chain are discussed with reference to evolution and phylogeny. The results show that the order Columbiformes is evolutionarily closer to the order Anseriformes. Since the pigeon is homogeneous, having HbA (alpha A-chain) and lacks alpha D-chain, its phylogenetic placement could be established among birds having single hemoglobin components.

Amino Acid Sequence↗