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At least 631 records · Page 35Linked to original sources
PubMed2000

A distinct seven-residue trigger sequence is indispensable for proper coiled-coil formation of the human macrophage scavenger receptor oligomerization domain.

We have recently identified a distinct 13-residue sequence pattern that occurs with limited sequence variations in many two-stranded coiled coils but not in trimers, tetramers, or pentamers. This coiled-coil trigger pattern was demonstrated to be indispensable for the assembly of the oligomerization domain of the actin-bundling protein cortexillin I from Dictyostelium discoideum and the leucine zipper domain of the yeast transcriptional activator GCN4. With the aim to extend our knowledge on trigger sequences we have investigated the human macrophage scavenger receptor type A oligomerization domain as a representative of three-stranded coiled coils. We prepared a variety of recombinant N- and C-terminal deletion mutants from the full-length oligomerization domain by heterologous gene expression in Escherichia coli and assessed their ability to form trimeric coiled-coil structures by circular dichroism spectroscopy and analytical ultracentrifugation. Deletion mapping identified a distinct seven-residue sequence that was absolutely required for proper coiled-coil formation, supporting our previous results that heptad repeats alone are not sufficient for oligomerization. The finding that all fragments containing this particular sequence exhibited similar thermal stabilities indicates primarily a stabilizing function of the coiled-coil trigger. Based on sequence similarity, we suggest that functionally related sites are present in other three-stranded coiled-coil proteins.

Amino Acid Sequence↗
PubMed1984

Assembly pathway of newly synthesized LamB protein an outer membrane protein of Escherichia coli K-12.

The assembly of newly induced LamB protein (phage lambda receptor) was investigated in an operon fusion strain of Escherichia coli, in which the lamB gene is expressed under lac promoter control. The induction kinetics both for total cellular and for cell surface-exposed LamB protein were studied by immunochemical detection methods, using two distinct antisera directed against detergent-solubilized LamB trimers and completely denatured LamB monomers, respectively. Anti-trimer antibodies recognized both monomers and trimers, whereas anti-monomer antibodies only reacted with monomers. Provided appropriate solubilization conditions were used, both antisera were able to immunoprecipitate intracellular mature LamB protein quantitatively. Following induction, the first LamB antigenic determinants were detected after 60 to 80 seconds; detection of the newly synthesized protein by anti-monomer antibodies slightly preceded that by anti-trimer antibodies, a finding that could be partly explained by the observation that anti-monomer antibodies recognized a larger fraction of nascent LamB than did anti-trimer antibodies. Exposure of antigenic determinants at the cell surface was delayed for 30 to 50 seconds with respect to their synthesis. Therefore, either translocation or conformational changes must be rate-limiting in the series of processes that eventually convert the newly synthesized protein into its mature outer membrane state. LamB protein was found to occur in at least three clearly distinguishable states. State I is the LamB monomer, state II corresponds to a metastable trimer that dissociates in sodium dodecyl sulphate above 60 degrees C, and state III is the state LamB trimer that dissociates in sodium dodecyl sulphate only at temperatures above 90 degrees C. The chase kinetics of these states showed that conversion of newly synthesized LamB monomers to stable LamB trimers occurred in two stages: state I monomers were chased into metastable state II trimers rapidly (t 1/2 = 20 s), whereas stabilization of state II trimers to state III trimers was a relatively slow (t 1/2 = 5.7 min) process. Based on our results, a timing sequence in the assembly of outer membrane LamB protein is proposed.

Bacterial Outer Membrane Proteins↗
PubMed1999

The folding and assembly of the dodecameric type II dehydroquinases.

The dodecameric type II dehydroquinases (DHQases) have an unusual quaternary structure in which four trimeric units are arranged with cubic 23 symmetry. The unfolding and refolding behaviour of the enzymes from Streptomyces coelicolor and Mycobacterium tuberculosis have been studied. Gel-permeation studies show that, at low concentrations (0.5 M) of guanidinium chloride (GdmCl), both enzymes dissociate into trimeric units, with little or no change in the secondary or tertiary structure and with a 15% loss (S. coelicolor) or a 55% increase (M. tuberculosis) in activity. At higher concentrations of GdmCl, both enzymes undergo sharp unfolding transitions over narrow ranges of the denaturant concentration, consistent with co-operative unfolding of the subunits. When the concentration of GdmCl is lowered by dilution from 6 M to 0.55 M, the enzyme from S. coelicolor refolds in an efficient manner to form trimeric units, with more than 75% regain of activity. Using a similar approach the M. tuberculosis enzyme regains less than 35% activity. From the time courses of the changes in CD, fluorescence and activity of the S. coelicolor enzyme, an outline model for the refolding of the enzyme has been proposed. The model involves a rapid refolding event in which approximately half the secondary structure is regained. A slower folding process follows within the monomer, resulting in acquisition of the full secondary structure. The major changes in fluorescence occur in a second-order process which involves the association of two folded monomers. Regain of activity is dependent on a further associative event, showing that the minimum active unit must be at least trimeric. Reassembly of the dodecameric S. coelicolor enzyme and essentially complete regain of activity can be accomplished if the denatured enzyme is dialysed extensively to remove GdmCl. These results are discussed in terms of the recently solved X-ray structures of type II DHQases from these sources.

Bacterial Proteins↗
PubMed2006

Effects of secreted oligomers of amyloid beta-protein on hippocampal synaptic plasticity: a potent role for trimers.

The accumulation of amyloid beta-protein (Abeta) in brain regions serving memory and cognition is a central pathogenic feature of Alzheimer's disease (AD). We have shown that small soluble oligomers of human Abeta that are naturally secreted by cultured cells inhibit hippocampal long-term potentiation (LTP) in vitro and in vivo and transiently impair the recall of a complex learned behaviour in rats. These results support the hypothesis that diffusible oligomers of Abeta initiate a synaptic dysfunction that may be an early event in AD. We now report detailed electrophysiological analyses that define conditions under which acute application of soluble Abeta inhibits hippocampal synaptic plasticity in wild-type mice. To ascertain which Abeta assemblies contribute to the impairment of LTP, we fractionated oligomers by size-exclusion chromatography and found that Abeta trimers fully inhibit LTP, whereas dimers and tetramers have an intermediate potency. Natural Abeta oligomers are sensitive to heat denaturation, primarily inhibit the induction phase of LTP, and cause a sustained impairment of LTP even after extensive washout. We observed no effects of Abeta oligomers on presynaptic vesicle release. LTP in juvenile mice is resistant to the effects of Abeta oligomers, as is brain-derived-neurotrophic-factor-induced LTP in adult hippocampus. We conclude that specific assemblies, particularly timers, of naturally secreted Abeta oligomers are potent and selective inhibitors of certain forms of hippocampal LTP.

Amyloid beta-Peptides↗
PubMed2003

Mutational analysis of human papillomavirus type 16 major capsid protein L1: the cysteines affecting the intermolecular bonding and structure of L1-capsids.

Human papillomavirus 16 major capsid protein L1 (composed of 505 amino acids (aa) including 12 cysteines) assembles by itself into virion-like icosahedral particles (L1-capsids), each of which is dissociated into 72 pentameric capsomeres when intermolecular disulfide bonds are disrupted. To identify the cysteines affecting the bonding and the structural integrity of the L1-capsids, we constructed a series of L1 mutants with substitution of serine for cysteine, which were expressed from recombinant baculoviruses in the insect Sf9 cells. From infected cells, the self-assembled L1-capsid fractions were purified by CsCl-equilibrium centrifugation and examined for velocity sedimentation profiles, for the presence of intermolecular bonding by SDS-PAGE with or without a reducing agent, for morphology under an electron microscope, and for susceptibility to trypsin digestion. Mutants C175S (C at aa 175 was replaced with S) and C185S were sedimented in sucrose-density gradients slightly slower than the wild type (WT) capsids, and mutant C428S stayed near the top as WT-capsomeres did. In the nonreducing SDS gel, where WT-capsids were separated into two bands of L1-trimers and L1-dimers, the C175S-trimer band was not detected, the C185S-dimer band was much less dense, and the C428S-trimer and C428S-dimer bands were not detected. Thus, it seems likely that C175, C185, and C428 are involved in L1 trimerization, in L1 dimerization, and in both, respectively. Morphologically, the C175S, C185S, and C428S fractions appeared to consist mostly of heterogeneous rod-shaped tubules, of smaller spherical particles, and of only capsomeres, respectively, whereas C102S, C229S, and C379S resembled WT. The C161S, C175S, C185S, C229S, C379S, and C428S capsids were more sensitive to degradation caused by trypsin than WT. The results indicate that C175, C185, and C428 are required for the normal assembly of L1-capsids through trimerization and dimerization of L1 bound by the intercapsomeric disulfide bonds between cysteines, and that C161, C229, and C379 are necessary for the integrity of L1-capsids probably through intramolecular bonding.

Amino Acid Substitution↗
PubMed2000

Addition of C-terminal histidyl tags to PsaL and PsaK1 proteins of cyanobacterial photosystem I.

In vitro mutagenesis was used to produce two photosystem I mutants of the cyanobacterium Synechocystis sp. PCC 6803. The mutant HK and HL contained hexahistidyl tags at the C-termini of the PsaK1 and PsaL subunits, respectively. The HK mutant contained wild-type amounts of trimeric PS I complexes, but the level of hexahistidine-tagged PsaK1 was found only ten per cent in the PS I complexes and membranes of the wild type level. Therefore, attachment of a tag at the C-terminus interferes with the expression or assembly of PsaK1. In contrast, the HL mutant contained a similar level of tagged PsaL as that in the wild type. However, trimeric PS I complexes could not be obtained from this strain, indicating that the C-terminus of PsaL is involved in the formation of PS I trimers. Hexahistidine-tagged complexes of the HL and HK strains could not be purified with Nickel-affinity chromatography, unless photosystem I was denatured with urea, demonstrating that tagged C-termini of PsaK1 and PsaL were embedded inside of the PS I complex. Protection of the C-terminus from trypsin cleavage further supported this conclusion. Thus, histidine tagging allowed us to demonstrate role of C-termini of two proteins of photosystem I.

Base Sequence↗
PubMed1996

The C-terminal domain of cartilage matrix protein assembles into a triple-stranded alpha-helical coiled-coil structure.

Cartilage matrix protein (CMP) is a major component of different cartilages and consists of a disulfide-linked homotrimer. To test whether the C-terminal region forms a three-stranded alpha-helical coiled-coil, we synthesized a peptide, CMP-C36, corresponding to the last 36 residues of human CMP. Analytical ultracentrifugation revealed that CMP-C36 forms a homotrimer under physiological conditions. The sedimentation coefficient of 1.12 S is consistent with a rod-shaped molecule of 5.8 nm length, suggesting a lateral packing of three peptide chains. Depending on conditions, circular dichroism spectroscopy showed 75 to 96% alpha-helical content. The shapes of the spectra are characteristic for a coiled-coil structure. Thermal and guanidine-HCI-induced denaturation revealed a high degree of cooperativity and high stability. The concentration dependence of the melting temperature suggest a two-state transition. The trimer is stabilized by increasing the ionic strength above 130 mM salt, above which six ions are released upon unfolding. The peptide characteristics make it very likely that the C-terminal domain serves as the trimerization site of CMP. The two cysteine residues preceding this sequence region might stabilize the complex after assembly.

Amino Acid Sequence↗
PubMed1976

Substructure and in vitro assembly of the outer, structured layer of Spirillum serpens.

Electron micrographs of disintegrating units of the outer, structured (HP) layer of Spirillum serpens and of the isolated protein obtained from the HP layer revealed V- and Y-shaped and linear profiles. Interpretation of these forms, influenced by the seemingly trimeric form of the isolated protein and by biochemical data, suggested that the protein subunits were identical and Y shaped. A model is proposed for the assembly of the Y-shaped subunits to form a hexagon composed of two triads (three Y-shaped subunits each). The isolated protein adsorbed to a template of wall fragments (basal layer) to the same degree (over 90%) in high concentrations of Na+, K+ (5 X 10(-2) M), Ca2+, Sr2+, and Mg2+ (10(-2) M). At a lower concentration (4 x 10(-5) M) of the cations there was differential adsorption of the protein. Adsorption to the template in the presence of each cation, followed by dilution, also led to differential release of the protein. The adsorption of the protein to the basal layer was correlated with reassembly of the HP layer on the template. The mechanisms seem to be: (i) an ionic strength-dependent reassembly, which results in an HP layer loosely attached to the template (this layer is easily dissociated by decreasing the ionic strength); and (ii) a cation-specific (Ca2+ or Sr2+, but not Mg2+, Na+, or K+) mechanism independent of ionic strength. In this latter case, the specific cations presumably form strong noncovalent "salt" linkages between triads and the basal layer, enabling stable hexagons and the HP layer to be formed.

Adsorption↗
PubMed1998

Folding and function of repetitive structure in the homotrimeric phage P22 tailspike protein.

The Salmonella bacteriophage P22 recognizes its host cell receptor, lipopolysaccharide, by means of six tailspikes, thermostable homotrimers of 72-kDa polypeptides. Biophysical results on the binding reaction, together with high-resolution structural information from X-ray crystallography, have shed light on the interactions determining the viral host range. Folding and assembly of the tailspike protein in vitro have been analyzed in detail, and the data have been compared with observations on the in vivo assembly pathway. Repetitive structural elements in the tailspike protein, like a side-by-side trimer of parallel beta-helices, a parallel alpha-helical bundle, a triangular prism made up from antiparallel beta-sheets, and a short segment of a triple beta-helix can be considered building blocks for larger structural proteins, and thus, the results on P22 tailspike may have implications for fibrous protein structure and folding.

Bacteriophage P22↗
PubMed2001

Disulfide bonds stabilize JC virus capsid-like structure by protecting calcium ions from chelation.

To investigate the role of disulfide bonds in the capsid structure, a recombinant JC virus-like particle (VLP) was used. The major capsid protein, VP1, of the JC virus was expressed in yeast cells. The yeast-expressed VP1 was self-assembled into a VLP. Disulfide bonds were found in the VLP which caused dimeric and trimeric VP1 linkages as demonstrated by non-reducing SDS-PAGE. The VLP remained intact when disulfide bonds were reduced by dithiothreitol. The VLP without disulfide bonds could be disassembled into capsomeres by EGTA alone, but those with disulfide bonds could not be disassembled by EGTA. Capsomeres were reassembled into VLPs in the presence of calcium ions. Capsomeres formed irregular aggregations instead of VLPs when treated with diamide to reconstitute the disulfide bonds. These results indicate that disulfide bonds play an important role in maintaining the integrity of the JC VLP by protecting calcium ions from chelation.

Calcium↗
PubMed1994

Discovery of nanomolar ligands for 7-transmembrane G-protein-coupled receptors from a diverse N-(substituted)glycine peptoid library.

Screening a diverse, combinatorial library of ca. 5000 synthetic dimer and trimer N-(substituted)glycine "peptides" yielded novel, high-affinity ligands for 7-transmembrane G-protein-coupled receptors. The peptoid library was efficiently assembled using readily available chemical building blocks. The choice of side chains was biased to resemble known ligands to 7-transmembrane G-protein-coupled receptors. All peptides were screened in solution-phase, competitive radioligand-binding assays. Peptoid trimer CHIR 2279 binds to the alpha 1-adrenergic receptor with a Ki of 5 nM, and trimer CHIR 4531 binds to the mu-opiate receptor with a Ki of 6 nM. This represents the first example of the discovery of high-affinity receptor ligands from a combinatorial library of non-natural chemical entities.

Amino Acid Sequence↗
PubMed1995

Purification and characterization of the imidazoleglycerol-phosphate dehydratase of Saccharomyces cerevisiae from recombinant Escherichia coli.

The HIS3+ gene of Saccharomyces cerevisiae was overexpressed in Escherichia coli and the recombinant imidazoleglycerol-phosphate dehydratase (IGPD) purified to homogeneity. Laser-desorption and electrospray m.s. indicated a molecular ion within 2 units of that expected (23833.3) on the basis of the protein sequence, with about half of the polypeptide lacking the N-terminal formylmethionine residue. IGPD initially purified as an apoprotein was catalytically inactive and mainly a trimer of M(r) 70,000. Addition of Mn2+ (but not Mg2+) caused this to assemble to an active (40 units/mg) enzyme (Mn-IGPD) comprising of 24 subunits (M(r) 573,000) and containing 1.35 +/- 0.1 Mn atoms/polypeptide subunit. An enzyme with an identical activity and metal content was also obtained when the fermenter growth medium of recombinant Escherichia coli was supplemented with MnCl2, and IGPD was purified through as Mn-IGPD rather than as the apoenzyme and assembled in vitro. Inhibition by EDTA indicated that the intrinsic Mn2+ was essential for activity. The retention of activity over time after dilution to very low concentrations of enzyme (< 20 nM) indicated that the metal remained in tight association with the protein. A novel continuous assay method was developed to facilitate the kinetic characterization of Mn-IGPD. At pH 7.0, the Km for IGP was 0.10 +/- 0.02 mM and the Ki value for inhibition by 1,2,4-triazole, 0.12 +/- 0.02 mM. In contrast with other reports, thiols had no influence on catalytic activity. The activity of Mn-IGPD varied with enzyme concentration in such a way as to suggest that it dissociates to a less active form at very low concentrations. Significant inhibition by the product, imidazole acetol phosphate, was inferred from the shape of the progress curve. Titration with, the potent competitive inhibitor, 2-hydroxy-3-(1,2,4-triazol-1-yl)propyl phosphonate indicated that Mn-IGPD contained 0.9 +/- 0.1 catalytic sites/protomer. The activity nearly doubled in the presence of high concentrations of Mn2+; the apparent Ks for stimulation was 20 microM. The basis of this effect was obscure, since there was no corresponding increase in the titre of active sites. Neither was there a discernable shift in the values of Km or Ki (above), although exogenous Mn2+ did reduce the optimum pH for kcat, from 7.2 to 6.8. On the basis of a single site/subunit, the maximum rate of catalytic turnover at 30 degrees C was 32 s-1.

Amino Acid Sequence↗
PubMed1989

Initiation of replication of the human hepatitis delta virus genome from cloned DNA: role of delta antigen.

Beginning with three partial cDNA clones of the RNA genome of human hepatitis delta virus (HDV), we assembled the complete 1,679-base sequence on a single molecule and then inserted a trimer of this into plasmid pSLV, a simian virus 40-based eucaryotic expression vector. This construct was used to transfect both monkey kidney (COS7) and human hepatocellular carcinoma (HuH7) cell lines. In this way we obtained replication of the HDV RNA genome and the appearance, in the nucleoli, of the delta antigen, the only known virus-coded protein. This proved both that the HDV genome could replicate in nonliver as well as liver cells and that there was no requirement for the presence of hepatitis B virus sequences or proteins. When the pSVL construct was made with a dimer of an HDV sequence with a 2-base-pair deletion in the open reading frame, genome replication was reduced at least 40-fold. However, when we cotransfected with a plasmid that expressed the correct delta antigen, the mutated dimer achieved a level of genome replication comparable to that of the nonmutated sequence. We thus conclude that the delta antigen can act in trans and is essential for replication of the HDV genome.

Antigens, Viral↗
PubMed2000

Conformational analysis and stability of collagen peptides by CD and by 1H- and 13C-NMR spectroscopies.

Four small type I collagen CNBr peptides containing complete natural sequences were purified from bovine skin and investigated by CD and 1H- and 13C-nmr spectroscopies to obtain information concerning their conformation and thermal stability. CD showed that a triple helix was formed at 10 degrees C in acidic aqueous solution by peptide alpha l(I) CB2 only, and to lesser extent, by alpha 1(I) CB4, whereas peptides alpha 1(I) CB5 and alpha 2(I) CB2 remained unstructured. Analytical gel filtration confirmed that peptides alpha 1(I) CB2 and alpha 1(I) CB4 only were able to form trimeric species at temperature between 14 and 20 degrees C, and indicated that the monomer = trimer equilibrium was influenced by the chaotropic nature of the salt present in the eluent, by its concentration, and by temperature variations. CD measurements at increasing temperatures showed that alpha 1(I) CB2 was less stable than its synthetic counterpart due to incomplete prolyl hydroxylation of the preparation from the natural source. 1H- and 13C-nmr spectra acquired in the temperature range 0-47 and 0-27 degrees C, respectively, indicated that with decreasing temperature the most abundant from of alpha 1(I) CB2 was in slow exchange with an assembled form, characterized by broad lines, as expected for the triple-helical conformation. A large number of trimer cross peaks was observed both in the proton and carbon spectra, and these were most likely due to the nonequivalence of the environments of the three chains in the triple helix. This nonequivalence may have implications for the aggregation of collagen molecules and for collagen binding to other molecules. The thermal transition from trimer to monomer was also monitored by 1H-nmr following the change in area of the signal belonging to one of the two beta protons of the C-terminal homoserine. The unfolding process was found to be fully reversible with a melting temperature of 13.4 degrees C, in agreement with CD results. The qualitative superposition of the melting curves obtained by CD for the peptide bond characteristics and by nmr for a side chain suggests that triple-helical backbone and side chains constitute a single unit.

Amino Acid Sequence↗
PubMed2005

Deformation of a "rigid" molecule in self-assembled nanostructures.

A simple spirobifluorene molecule with pseudotetrahedral structure was investigated for its supposed conformational resilience upon adsorption. Through deposition at room temperature of this molecule on a Cu(111) surface and subsequent observation at 5 K with an ultrahigh vacuum scanning tunneling microscope, this "rigidity" upon physisorption is confirmed. However, an unexpected chemisorbed state was also found with the molecules arranged in trimers. The unique coexistence of physisorbed and chemisorbed states on the same substrate is thus demonstrated at the early stage of self-assembly.

Journal Article↗
PubMed2006

Functions of the stem region of the Semliki Forest virus fusion protein during virus fusion and assembly.

Membrane fusion of the alphaviruses is mediated by the E1 protein, a class II virus membrane fusion protein. During fusion, E1 dissociates from its heterodimer interaction with the E2 protein and forms a target membrane-inserted E1 homotrimer. The structure of the homotrimer is that of a trimeric hairpin in which E1 domain III and the stem region fold back toward the target membrane-inserted fusion peptide loop. The E1 stem region has a strictly conserved length and several highly conserved residues, suggesting the possibility of specific stem interactions along the trimer core and an important role in driving membrane fusion. Mutagenesis studies of the alphavirus Semliki Forest virus (SFV) here demonstrated that there was a strong requirement for the E1 stem in virus assembly and budding, probably reflecting its importance in lateral interactions of the envelope proteins. Surprisingly, however, neither the conserved length nor any specific residues of the stem were required for membrane fusion. Although the highest fusion activity was observed with wild-type E1, efficient fusion was mediated by stem mutants containing a variety of substitutions or deletions. A minimal stem length was required but could be conferred by a series of alanine residues. The lack of a specific stem sequence requirement during SFV fusion suggests that the interaction of domain III with the trimer core can provide sufficient driving force to mediate membrane merger.

Amino Acid Sequence↗
PubMed1997

Distinct roles of mouse laminin beta1 long arm domains for alpha1beta1gamma1 trimer formation.

Mouse embryonal carcinoma F9 cells expressing partial mouse laminin beta1 covering either the C-terminal end (delta beta1S) or the whole (delta beta1L) of the long arm were established to study the assembly and interchain disulfide-bonding of beta1 to endogenous laminin alpha1 and gamma1. Both delta beta1S and delta beta1L were disulfide-bonded to gamma1 but only delta beta1L gamma1 dimer formed a disulfide-bonded alpha1 delta beta1L gamma1 trimer which was actively secreted into the medium. Meanwhile, in the cells producing delta beta1S gamma1 dimer, the level of endogenous alpha1 beta1 gamma1 was reduced but the level of monomeric alpha1 was increased, suggesting that alpha1 was recruited to trimer formation with the delta beta1S gamma1 dimer without disulfide-bonding. This shows that the delta beta1S gamma1 dimer can associate with alpha1 but not support the disulfide-bonding at the N-terminus of the long arm of alpha1. While control cells secrete neither monomeric alpha1 nor the beta1gamma1 dimer into the medium, the delta beta1S gamma1 producing cells probably do as alpha1 delta beta1 gamma1 trimer. We thus propose that the N- and C-termini of the long arm of laminin beta1 have distinct roles for trimer formation.

Animals↗
PubMed1980

Application of calculated sedimentation ratios in the specification of models for protein dimers, trimers, tetramers and pentamers.

In the preceding paper a systematic method for delineating quaternary structures compatible with the sedimentation behaviour of oligomeric assemblies was developed. In this companion paper the approach is illustrated by its application to a number of oligomeric proteins, namely beta-lactoglobulin, aminoacyl transferase, succinic semialdehyde dehydrogenase, arginine decarboxylase, and the arthropod hemocyanins. Structures of these proteins based on comparisons of calculated and experimental sedimentation coefficients are presented and, wherever possible, compared with those obtained by other techniques. The usefulness and limitations of the method are assessed. It is concluded that the sedimentation analysis will usually yield a reasonably good representation of the mode of assembly of protein molecules in oligomeric structures if accurate experimental data are available. A high degree of resolution of structural detail is not expected and since, in addition, the sedimentation ratio method is seldom definitive to one structure, it is most valuable when used in a conformatory or eliminative way with results from techniques more specifically designed for structure determination.

Journal Article↗