A peptide representing the carboxyl-terminal tail of the met receptor inhibits kinase activity and invasive growth

Interaction of the hepatocyte growth factor (HGF) with its receptor, the Met tyrosine kinase, results in invasive growth, a genetic program essential to embryonic development and implicated in tumor metastasis. Met-mediated invasive growth requires autophosphorylation of the receptor on tyrosines located in the kinase activation loop (Tyr(1234)-Tyr(1235)) and in the carboxyl-terminal tail (Tyr(1349)-Tyr(1356)). We report that peptides derived from the Met receptor tail, but not from the activation loop, bind the receptor and inhibit the kinase activity in vitro. Cell delivery of the tail receptor peptide impairs HGF-dependent Met phosphorylation and downstream signaling. In normal and transformed epithelial cells, the tail receptor peptide inhibits HGF-mediated invasive growth, as measured by cell migration, invasiveness, and branched morphogenesis. The Met tail peptide inhibits the closely related Ron receptor but does not significantly affect the epidermal growth factor, platelet-derived growth factor, or vascular endothelial growth factor receptor activities. These experiments show that carboxyl-terminal sequences impair the catalytic properties of the Met receptor, thus suggesting that in the resting state the nonphosphorylated tail acts as an intramolecular modulator. Furthermore, they provide a strategy to selectively target the MET proto-oncogene by using small, cell-permeable, peptide derivatives.

Hydrolysis by somatic angiotensin-I converting enzyme of basic dipeptides from a cholecystokinin/gastrin and a LH-RH peptide extended at the C-terminus with gly-Arg/Lys-arg, but not from diarginyl insulin

Endoproteolytic cleavage of protein prohormones often generates intermediates extended at the C-terminus by Arg-Arg or Lys-Arg, the removal of which by a carboxypeptidase (CPE) is normally an important step in the maturation of many peptide hormones. Recent studies in mice that lack CP activity indicate the existence of alternative tissue or plasma enzymes capable of removing C-terminal basic residues from prohormone intermediates. Using inhibitors of angiotensin I-converting enzyme (ACE) and CP, we show that both these enzymes in mouse serum can remove the basic amino acids from the C-terminus of CCK5-GRR and LH-RH-GKR, but only CP is responsible for converting diarginyl insulin to insulin. ACE activity removes C-terminal dipeptides to generate the Gly-extended peptides, whereas CP hydrolysis gives rise to CCK5-GR and LH-RH-GK, both of which are susceptible to the dipeptidyl carboxypeptidase activity of ACE. Somatic ACE has two similar protein domains (the N-domain and the C-domain), each with an active site that can display different substrate specificities. CCK5-GRR is a high-affinity substrate for both the N-domain and C-domain active sites of human sACE (Km of 9.4 microm and 9.0 microm, respectively) with the N-domain showing greater efficiency (kcat : Km ratio of 2.6 in favour of the N-domain). We conclude that somatic forms of ACE should be considered as alternatives to CPs for the removal of basic residues from some Arg/Lys-extended peptides.

Rapid gas chromatographic analysis of drugs of forensic interest

High-speed gas chromatographic (GC) screening for drugs of forensic relevance is performed using a commercial Flash GC instrument in which the chromatographic column is resistively heated at rates of up to 30 degrees C/s. Temperature programming conditions are varied in an experiment designed to evaluate trade-offs between resolution and analysis time for a mixture of 19 drugs of abuse. All 19 components can be separated with excellent resolution in 90 s. Specific analytes can be analyzed even faster; for example, amphetamine analysis is completed in less than 20 s. Case studies of confiscated street drugs containing amphetamine, cocaine, and heroin are analyzed to evaluate the retention time repeatability. Ten replicate injections over a 2-day period for 3 different drug samples achieved retention time relative standard deviations in the range of 0.48 to 0.81%.

The Drosophila melanogaster-related angiotensin-I-converting enzymes Acer and Ance--distinct enzymic characteristics and alternative expression during pupal development

Drosophila melanogaster express two distinct angiotensin-I-converting enzymes (ACEs) called Ance and Acer, which display a high level of primary structure similarity. We have expressed Acer in the yeast Pichia pastoris and purified the recombinant enzyme with a view to developing biochemical tools to distinguish between Acer and Ance. Purified Acer and Ance expressed in yeast were used to raise anti-Acer Ig and anti-Ance Ig that specifically cross-reacted with the respective enzyme on immunoblotting, but did not act as specific inhibitors. Acer cleaves the C-terminal dipeptides from benzoylglycyl-histidyl-leucine and [Leu5]enkephalin, and Acer and Ance are both able to act as endopeptidases, releasing the C-terminal dipeptideamide from [Leu5]enkephalinamide. However, Acer hydrolyses this substrate at a slightly faster rate than [Leu5]enkephalin, whereas Ance hydrolyses the peptide with a free C-terminus with a kcat 15-fold higher than [Leu5]enkephalinamide. In addition, Acer did not cleave angiotensin I. In contrast, Ance hydrolysed 25% of this substrate at an 8-fold lower enzyme concentration. Furthermore, Acer did not hydrolyse the synthetic substrates Phe-Ser-Pro-Arg-Leu-Gly-Arg-Arg and Phe-Ser-Pro-Arg-Leu-Gly-Lys-Arg, two partially processed putative locustamyotropin precursors, under conditions where Ance produced 82% substrate hydrolysis. Acer was inhibited by captopril, trandolaprilat and enalaprilat, with apparent Ki values in the nanomolar range, whereas lisinopril and fosinoprilat were less potent. We show that the two Drosophila ACEs are alternatively expressed in stages P1 (white puparium)-P15 (eclosion) of pupal development; Ance is expressed predominantly during stages P4-P7, whereas the ACE activity expressed during stages P9-P12 is mainly due to Acer suggesting different roles for the two enzymes during pupal development.

A novel peptide-processing activity of insect peptidyl-dipeptidase A (angiotensin I-converting enzyme): the hydrolysis of lysyl-arginine and arginyl-arginine from the C-terminus of an insect prohormone peptide

Insect peptidyl-dipeptidase A [angiotensin I-converting enzyme (ACE)] is a soluble single-domain peptidyl-dipeptidase that has many properties in common with the C-domain of mammalian somatic ACE and with the single-domain mammalian germinal ACE. Mammalian somatic ACE is important in blood homoeostasis, but the role of ACE in insects is not known. Immunocytochemistry has been used to localize ACE in the neuroendocrine system of the locust, Locusta migratoria. Staining was observed in five groups of neurosecretory cells in the brain and suboesophageal ganglion, in the nervi corpori cardiaci, the storage part of the corpora cardiaca and in the nervi corpori allati. In three groups of neurosecretory cells, ACE co-localized with locustamyotropins, suggesting a possible role for the enzyme in the metabolism of these neuropeptides. We demonstrate in vitro a novel activity of ACE that removes pairs of basic amino acid residues from a locustamyotropin peptide extended at the C-terminus with either Gly-Lys-Arg or Gly-Arg-Arg, corresponding to a consensus recognition sequence for endoproteolysis of prohormone proteins by prohormone convertases. The low Km and high kcat values (Km 7.3 and 5.0 microM, kcat 226 and 207 s-1 for the hydrolysis of Phe-Ser-Pro-Arg-Leu-Gly-Lys-Arg and Phe-Ser-Pro-Arg-Leu-Gly-Arg-Arg, respectively) obtained for the hydrolysis of these two peptides by insect ACE means that these peptides, along with mammalian bradykinin, are the most favoured in vitro ACE substrates so far identified. The discovery of this in vitro prohormone-processing activity of insect ACE provides a possible explanation for the intracellular co-localization of the enzyme with locustamyotropin peptides, and provides evidence for a new role for ACE in the biosynthesis of peptide hormones and transmitters.

Distalless expression in crustaceans and the patterning of branched limbs

In Drosophila, Distalless (Dll) is critical in establishing the proximal/distal axis of the leg. Lack of proper Dll expression causes distal limb structures to be truncated or lost. Dll expression was examined through the course of development in the limbs of two crustaceans, Triops and Nebalia. Because the limbs of these two species are branched, they provide a comparison to the uniramous (unbranched) leg of Drosophila. In Triops and Nebalia, development of limb branches is not tightly coupled with Dll expression: in some cases, branches can arise prior to Dll expression and in others, certain branches never express Dll. These data suggest that, while Dll may indeed initiate overall limb outgrowth, limb branches are unlikely to be patterned by a simple iteration of the mechanism patterning the unbranched leg of Drosophila.

Cleavage of arginyl-arginine and lysyl-arginine from the C-terminus of pro-hormone peptides by human germinal angiotensin I-converting enzyme (ACE) and the C-domain of human somatic ACE

Mammalian germinal angiotensin I-converting enzyme (gACE) is a single-domain dipeptidyl carboxypeptidase found exclusively in male germ cells, which has almost identical sequence and enzymic properties with the C-domain of the two-domain somatic ACE. Mutant mice that do not express gACE are infertile, suggesting a role for the enzyme in the processing of undefined peptides involved in fertilization. A number of spermatid peptides [e.g. cholecystokinin (CCK) and gastrin] are processed from pro-hormones by endo- and exo-proteolytic cleavages which might generate substrates for gACE. We have shown that peptide hormone intermediates with Lys/Arg-Arg at the C-terminus are high-affinity substrates for human gACE. gACE from human sperm cleaved Arg-Arg from the C-terminus of the CCK5-GRR (GWMDFGRR), a peptide corresponding to the C-terminus of a CCK-gastrin prohormone intermediate. Hydrolysis of CCK5-GRR by recombinant human C-domain ACE was Cl- dependent, with maximal activity achieved in 5-10 mM NaCl at pH 6.4. C-Domain ACE cleaved Lys/Arg-Arg from the C-terminus of dynorphin-(1-7), a pro-TRH peptide KRQHPGKR, and two insect peptides FSPRLGKR and FSPRLGRR. C-Domain ACE displayed high affinity towards all these substrates with Vmax/Km values between 14 and 113 times greater than the Vmax/Km for the conversion of the best known ACE substrate, angiotensin I, into angiotensin II. In conclusion, we have identified a new class of substrates for human gACE, and we suggest that gACE might be an alternative to carboxypeptidase E for the trimming of basic dipeptides from the C-terminus of intermediates generated from pro-hormones by subtilisin-like convertases in human male germ cells.

Substrate dependence of angiotensin I-converting enzyme inhibition: captopril displays a partial selectivity for inhibition of N-acetyl-seryl-aspartyl-lysyl-proline hydrolysis compared with that of angiotensin I

Angiotensin I-converting enzyme (ACE) is composed of two highly similar domains (referred to here as the N and C domains) that play a central role in blood pressure regulation; ACE inhibitors are widely used in the treatment of hypertension. However, the negative regulator of hematopoiesis, N-acetyl-seryl-aspartyl-lysyl-prolyl (AcSDKP), is a specific substrate of the N domain-active site; thus, in addition to the cardiovascular function of ACE, the enzyme may be involved in hematopoietic stem cell regulation, raising the interest of designing N domain-specific ACE inhibitors. We analyzed the inhibition of angiotensin I and AcSDKP hydrolysis as well as that of three synthetic ACE substrates by wild-type ACE and the N and C domains by using a range of specific ACE inhibitors. We demonstrate that captopril, lisinopril, and fosinoprilat are potent inhibitors of AcSDKP hydrolysis by wild-type ACE, with K(i) values in the subnanomolar range. However, of the inhibitors tested, captopril is the only compound able to differentiate to some degree between AcSDKP and angiotensin I inhibition of hydrolysis by wild-type ACE: the K(i) value with AcSDKP as substrate was 16-fold lower than that with angiotensin I as substrate. This raises the possibility of using captopril to enhance plasma AcSDKP levels with the aim of normal hematopoeitic stem cell protection during chemotherapy and a limited effect on the cardiovascular function of ACE.

Cleavage-secretion of angiotensin I-converting enzyme in yeast

Angiotensin I-converting enzyme (ACE) is a type I transmembrane protein composed of two domains (N and C domains) which undergoes a post-translational proteolytic cleavage in mammalian cells to release the soluble ectodomain. The protease involved in ACE cleavage-secretion (ACE-secretase) is not well characterised and eludes isolation: the presence of a yeast homologue, thus more amenable to genetic manipulation, would facilitate its identification. We have expressed a secreted form of the ACE C domain, lacking the C-terminal membrane anchor (C domain(deltaCOOH)), and the membrane-anchored C domain (C domain) in the yeast Pichia pastoris by fusion to prepro-alpha-factor. Immunofluorescent labelling localises the ACE C domain to the periphery of yeast cells but not C domain(deltaCOOH), however, expression of both C domain and C domain(deltaCOOH) produced soluble enzymes in the culture medium. Immunocharacterisation of the two soluble forms of the C domain indicates a proteolytic cleavage of the membrane-bound C domain to produce the soluble counterpart. Thus ACE undergoes a proteolytic cleavage in yeast.

Drosophila melanogaster angiotensin I-converting enzyme expressed in Pichia pastoris resembles the C domain of the mammalian homologue and does not require glycosylation for secretion and enzymic activity

Drosophila melanogaster angiotensin I-converting enzyme (AnCE) is a secreted single-domain homologue of mammalian angiotensin I-converting enzyme (ACE) which comprises two domains (N and C domains). In order to characterize in detail the enzymic properties of AnCE and to study the influence of glycosylation on the secretion and enzymic activity of this enzyme, we overexpressed AnCE (expression level, 160 mg/l) and an unglycosylated mutant (expression level, 43 mg/l) in the yeast Pichia pastoris. The recombinant enzyme was apparently homogeneous on SDS/PAGE without purification and partial deglycosylation demonstrated that all three potential sites for N-linked glycosylation were occupied by oligosaccharide chains. Each N-glycosylation sequence (Asn-Xaa-Ser/Thr) was disrupted by substituting a glutamine for the asparagine residue at amino acid positions 53, 196 and 311 by site-directed mutagenesis to produce a single mutant. Expression of the unglycosylated mutant in Pichia produced a secreted catalytically active enzyme (AnCE delta CHO). This mutant displayed unaltered kinetics for the hydrolyses of hippuryl-His-Leu, angiotensin 1 and N-acetyl-Ser-Asp-Lys-Pro (AcSDKP) and was equally sensitive to ACE inhibitors compared with wild-type AnCE. However, AnCE delta CHO was less stable, displaying a half-life of 4.94 h at 37 degrees C, compared with AnCE which retained full activity under the same conditions. Two catalytic criteria demonstrate the functional resemblance of AnCE with the human ACE C domain: first, the kcat/Km of AcSDKP hydrolysis and secondly, the kcat/Km and optimal chloride concentration for hippuryl-His-Leu hydrolysis. A range of ACE inhibitors were far less potent towards AnCE compared with the human ACE domains, except for captopril which suggests an alternative structure in AnCE corresponding to the region of the S1 subsite in the human ACE active sites.

A study of chimeras constructed with the two domains of angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE) is composed of two highly similar domains called the N and C domains, which display some contrasting enzymatic properties. We constructed two ACE chimeras: chimera 1, comprised of the N domain containing the central 60 amino acid residues of the C domain, and chimera 2, comprised of the C domain containing the central 60 amino acid residues of the N domain. Chimeras 1 and 2 displayed Km values for Hip-His-Leu and Z-Phe-His-Leu and kcat ratios for these two substrates similar to that of the N and C domains, respectively. Thus, the short sequence exchanged between the two domains does not confer the specific properties of that domain for these two substrates but, rather, such specific properties must arise from the sequences surrounding the central region in each domain.

Low vision rehabilitation for a patient with a traumatic brain injury

The client described in this article had undergone intensive rehabilitation for physical and cognitive deficits that resulted from an anoxic encephalopathy. Her recovery was good in all areas except visual functioning. Her reading and writing deficits were initially thought to result from visual-perceptual problems. A low vision evaluation identified the deficits as resulting from a macular visual field loss. Warren (1993) has proposed that an intact visual field is one of the basic components of vision that must be present before higher visual processing can occur. Until the macular perimetry was performed on this client, the extent of her central field loss was unknown, and the treatment that focused on the higher level visual processing was unsuccessful. The low vision program targeted the central field loss as the probable cause for her difficulties and an effective treatment protocol was established. The client was instructed regarding the nature of her visual field deficit and was trained in methods to compensate for this deficit. Although she has not returned to work as of this writing because of financial disincentives, the training resulted in a measurable and functional improvement in the client's ability to read continuous print text, a task she had not performed in 4 years, and in her ability to perform all writing tasks needed for daily living.

Recent advances in knowledge of the structure and function of the angiotensin I converting enzyme

AIM

To review the structure and function of the angiotensin I converting enzyme (ACE), focusing on recent results from studies using a wide range of molecular biological techniques.

ACE STRUCTURE AND FUNCTION

ACE is an ectoenzyme expressed as two isoenzymes in mammals, a larger somatic form found in endothelial, epithelial and neuronal tissues and a smaller form in germinal tissues. Both forms have similar enzymatic activities but differ in size and immunological properties. The somatic form of ACE is composed of two highly homologous domains (amino and carboxyl domains) while the germinal form contains only one domain. Somatic ACE has two functional catalytic sites, both dependent on a zinc cofactor. Each ACE domain has also been shown to interact differently with competitive inhibitors.

MECHANISM OF ACE ANCHORAGE AND SOLUBILIZATION

The mechanism for anchoring ACE to the cell membrane has also been reported, and the solubilization step outlined. The relationship between the membrane-bound and soluble forms has been investigated, and the physiological relevance of this mechanism discussed.

GENETIC STRUCTURE

The structure of the ACE gene has been determined and the distribution in cells and different tissues has been reported in various studies.

CONCLUSION

All results have indicated that there are important functional and structural differences between the two domains, but at present ACE cannot be considered a true bifunctional enzyme, even though an exclusive substrate has been identified for the amino domain.

Cloning and expression of an evolutionary conserved single-domain angiotensin converting enzyme from Drosophila melanogaster

Mammalian somatic angiotensin converting enzyme (EC 3.4.15.1, ACE) consists of two highly homologous (N- and C-) domains encoded by a duplicated gene. We have identified an apparent single-domain (67 kDa) insect angiotensin converting enzyme (AnCE) in embryos of Drosophila melanogaster which converts angiotensin I to angiotensin II (Km, 365 microM), removes Phe-Arg from the C terminus of bradykinin (Km, 22 microM), and is inhibited by ACE inhibitors, captopril (IC50 = 1.1 x 10(-9) M) and trandolaprilat (IC50 = 1.6 x 10(-8) M). We also report the cloning and expression of a Drosophila AnCE cDNA which codes for a single-domain 615-amino acid protein with a predicted 17-amino acid signal peptide and regions with high levels of homology to both the N- and C-domains of mammalian somatic ACE, especially around the active site consensus sequence. Northern analysis identified a single 2.1-kilobase mRNA in Drosophila embryos, and Southern analysis of Drosophila genomic DNA indicates that the insect gene is not duplicated. When expressed in COS-7 cells, the AnCE protein is a secreted enzyme, which converts angiotensin I to angiotensin II and is inhibited by captopril (IC50 = 5.6 x 10(-9) M) and trandolaprilat (IC50 = 2 x 10(-8) M). The evolutionary significance of these results is discussed.

Application of dispersion modeling to indoor gas release scenarios

Many complex models are available to study the dispersion of contaminants or ventilation effectiveness in indoor spaces. Because of the computationally complex numerical schemes employed, most of these models require mainframe computers or workstations. However, simple design tools or guidelines are needed, in addition to complicated models. A dispersion model based on the basic governing equations was developed and uses an analytical solution. Because the concentration is expressed by an analytical solution, the grid size and time steps are user definable. A computer program was used to obtain numerical results and to obtain release history from a thermodynamic source model. The model can be used to estimate three-dimensional spatial and temporal variations in concentrations resulting from transient gas releases in an enclosure. The model was used to study a gas release scenario from a pressurized cylinder into a large ventilated building, in this case, a transit parking and fueling facility.

A genetic study of angiotensin I-converting enzyme levels in human semen

The plasma level of angiotensin I-converting enzyme (ACE) has been shown to be under genetic control. An insertion/deletion polymorphism in the ACE gene is associated with differences in the level of ACE in the plasma and inside T-lymphocytes. An ACE isoform is present in large amounts in spermatozoa and is expressed under an alternative, germ cell-specific promoter, whereas ACE present in the seminal fluid is the somatic form of ACE. We have investigated the effect associated with the I/D polymorphism on the level of ACE in seminal fluid and in spermatozoa. No differences in the level of ACE measured in the seminal fluid or in the spermatozoa were associated with the ACE I/D genotypes. We conclude that the modulation of expression associated with the I/D polymorphism is restricted to the somatic ACE promoter. These results also suggest that if one allele modulating the expression of ACE was under positive selection pressure, it was not through an effect on the semen concentration of ACE.

Angiotensin I converting enzyme gene: regulation, polymorphism and implications in cardiovascular diseases

Angiotensin I converting enzyme (ACE), also called dipeptidyl-carboxypeptidase I (DCP I), is a zinc metallopeptidase widely distributed on the surface of endothelial and epithelial cells. Its role in the vasoactive peptide, the metabolism of the two active peptides, angiotensin and bradykinin, and the beneficial effects of its inhibition in cardiovascular diseases, have raised considerable interest in this enzyme. The potential implications of ACE gene polymorphism, which affects the expression of the gene in cardiovascular diseases, has been widely investigated. This review summarizes the results of these studies.

Identification of two active site residues in human angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE) contains two zinc-dependent catalytic domains (N and C domains) each bearing the motif HEXXH where the two histidines form two of the three amino acid zinc ligands. Sequence alignment of each ACE domain with other zinc metalloproteases, indicates a glutamate residues which putatively constitutes the third zinc ligand and an aspartate residue which may form an indirect zinc interaction. We investigated the functional roles of the glutamate and aspartate residues in the ACE C domain (Glu987 and Asp991) using a cDNA encoding an inactive N domain. We mutated Glu987 to aspartate (E987D) or valine (E987V) and Asp991 to glutamate (D991E) or alanine (D991A). Catalytically active mutants (E987D, D991E and D991A) exhibited similar Km values for hippuryl-His-Leu compared to non-mutated C domain. E987D displayed a 300-fold decrease in kcat and a 25-fold reduction in sensitivity to the ACE inhibitor trandolaprilat, whose binding is zinc-dependent. E987V was catalytically inactive and did not bind [3H]trandolaprilat. D991E and D991A exhibited a 3.8- and 22-fold decrease in kcat, respectively, and the Ki' values for trandolaprilat were increased 8- and 29-fold. These results provide strong evidence that Glu987 constitutes the third zinc ligand in the ACE C domain and suggest a role for Asp991 in positioning the C domain active site zinc ion.

A Model of Rowing Propulsion and the Ontogeny of Locomotion in Artemia Larvae

Newly hatched Artemia larvae use one pair of limbs to locomote. During development they gradually add additional limbs along the elongating trunk. As larvae grow, body length increases from about 0.4 mm to 4 mm, mean swimming speed increases from 1.8 mm s-1 to 9.9 mm s-1, and frequency of antennal beat decreases from 9.5 to 6.7 Hz. As new limbs are added, they become active in the metachronal rhythm of pre-existing limbs. The body velocity oscillates as early larvae swim; later larvae swim without a cyclic acceleration and deceleration of the body. The change in the pattern of swimming is correlated with the addition of propulsors and a transition in the relative importance of viscous and inertial effects that determine the propulsion in subsequent stages. Reynolds number (based on body length) increases from 2 to 37. A theoretical analysis of rowing propulsion at these intermediate Reynolds numbers shows that initial development of new limbs in Artemia larvae is unimportant for propulsion. Rowing propulsion at the low Reynolds numbers is drag-based; as Reynolds number increases, inertial effects become more important, and unsteady forces on the body become significant in the balance between limb and body. A glide of the body develops at the end of the powerstroke, and relative limb velocity changes.

Locomotion in Developing Artemia Larvae: Mechanical Analysis of Antennal Propulsors Based on Large-Scale Physical Models

A physical model of the swimming appendage (second antenna) of a larval Artemia was oscillated and translated through a tank of glycerine to determine how such a shape may be used to generate thrust at the intermediate Reynolds numbers at which it operates. Force on the model was measured by strain gauges and used to calculate coefficients of drag at a series of speeds and frequencies that represented flow regimes of different larval stages. Measured coefficients of drag (Cd) over this Reynolds number range ({approx}1-10) suggest that an expression for a cylinder perpendicular to flow at intermediate Reynolds number (Cd = 1 + 10 Re-2/3) best represents the changes in drag coefficients for this geometry. Unsteady forces were found to be a negligible portion of the force on the model in spite of a high ratio of frequency of oscillation to forward translational velocity (i.e., Strouhal number). Comparison of the thrust generated by the model with its fan of setae rigidly fixed versus passively flexing suggests that passive extension of setae can be influenced by relative limb and body speed.

A recombinant form of angiotensin converting enzyme expressed from baculovirus-infected insect cells

A secreted form of the C-domain of angiotensin converting enzyme has been expressed from the baculovirus-infected insect cell system. This soluble enzyme was purified by affinity chromatography and characterised in terms of its carbohydrate side chains and binding of substrates and inhibitors.