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Parry DAD. Structures of the ß-Keratin Filaments and Keratin Intermediate Filaments in the Epidermal Appendages of Birds and Reptiles (Sauropsids). Genes (Basel) 2021; 12:591. [PMID: 33920614 PMCID: PMC8072682 DOI: 10.3390/genes12040591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 01/14/2023] Open
Abstract
The epidermal appendages of birds and reptiles (the sauropsids) include claws, scales, and feathers. Each has specialized physical properties that facilitate movement, thermal insulation, defence mechanisms, and/or the catching of prey. The mechanical attributes of each of these appendages originate from its fibril-matrix texture, where the two filamentous structures present, i.e., the corneous ß-proteins (CBP or ß-keratins) that form 3.4 nm diameter filaments and the α-fibrous molecules that form the 7-10 nm diameter keratin intermediate filaments (KIF), provide much of the required tensile properties. The matrix, which is composed of the terminal domains of the KIF molecules and the proteins of the epidermal differentiation complex (EDC) (and which include the terminal domains of the CBP), provides the appendages, with their ability to resist compression and torsion. Only by knowing the detailed structures of the individual components and the manner in which they interact with one another will a full understanding be gained of the physical properties of the tissues as a whole. Towards that end, newly-derived aspects of the detailed conformations of the two filamentous structures will be discussed and then placed in the context of former knowledge.
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Affiliation(s)
- David A D Parry
- School of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand
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Chen IC, Yu J. Human Hair: Scaffold Materials for Regenerative Medicine. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1249:223-229. [PMID: 32602100 DOI: 10.1007/978-981-15-3258-0_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This chapter reviews the studies of keratin-based biomaterials in the past and discusses the advancement of it in recent years. Keratin, as a protein-based biopolymer, possesses excellent biocompatibility and biodegradability. In addition, keratin has abundant disulfide bonds, which result in its unique and tough structure. However, the property also results in dissolubility, which causes difficult process ability. Over the past years, much research utilizes different methodologies to extract keratins. Different kinds of extraction methods affect the characteristics of keratins and give a wide variety of application forms. The features of different methods are discussed and summarized in the following.
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Affiliation(s)
- I-Chun Chen
- Department of Chemical Engineering, National Taiwan University, Taipei City, Taiwan
| | - Jiashing Yu
- Department of Chemical Engineering, National Taiwan University, Taipei City, Taiwan.
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Direct evidence supporting the existence of a helical dislocation in protofilament packing in the intermediate filaments of oxidized trichocyte keratin. J Struct Biol 2018; 204:491-497. [PMID: 30248462 DOI: 10.1016/j.jsb.2018.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/29/2018] [Accepted: 09/19/2018] [Indexed: 11/20/2022]
Abstract
The X-ray diffraction patterns of quill and hair, as well as other trichocyte keratin appendages, contain meridional reflections that can be indexed on an axial repeat of 470 Å. Unusually, however, many of the expected orders are not observed. A possible explanation, proposed by Fraser and MacRae (1983), was that the intermediate filaments (IF) that constitute the fibrillar component of the filament/matrix texture consist of 4-chain protofilaments arranged on a surface lattice subject to a helical dislocation. The radial projection of the resulting 8-protofilament ribbon was defined in terms of a two-dimensional unit cell characterized by vectors (a, b) with axial projections za ∼ 74 Å and zb ∼ 198 Å. This situation resembles that found in microtubules, where helical dislocations in subunit packing are also encountered, leading to a so-called "seam" along their length (Metoz and Wade, 1997). In keratin, however, the protofilaments are helical so the seam is inclined to the axis of the IF. Here we report details of the Patterson function that provides independent evidence for both the helical dislocation and the dimensions of the surface lattice. In addition, the observed meridional X-ray amplitudes have been compared with those predicted by various models of the axial distribution of electron density. A new model, adapted from one previously proposed, fits the data significantly better than has heretofore proved possible. An interpretation of the model in terms of either specific keratin-associated-protein (KAP) binding or the retention of IF symmetry by a portion of the head and/or tail domains is suggested.
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Fraser RDB, Parry DAD. Structural Hierarchy of Trichocyte Keratin Intermediate Filaments. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1054:57-70. [PMID: 29797268 DOI: 10.1007/978-981-10-8195-8_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Although trichocyte keratins (hair, wool, quill, claw) have been studied since the 1930s it is only over the last 30 years or so that major advances have been made in our understanding of the complex structural hierarchy of the filamentous component of this important filament-matrix composite. A variety of techniques, including amino acid sequence analysis, computer modelling, X-ray fibre diffraction and protein crystallography, various forms of electron microscopy, and crosslinking methods have now combined to reveal much of the structural detail. The heterodimeric structure of the keratin molecule is clear, as are the highly-specific modes by which these molecules aggregate to form functionally viable IF. The observation that hair keratin can adopt not one but two structurally-distinct conformations, one formed in the living cells at the base of the hair follicle in a reducing environment and the second in the fully differentiated hair in dead cells in an oxidized state, was unexpected but has major implications for the mechanism of hair growth. Insights have also been made into the mechanism of the uppermost level of hair superstructure, relating to the assembly of the IF in the paracortical and orthocortical macrofibrils.
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Affiliation(s)
- R D Bruce Fraser
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,, Tewantin, QLD, Australia
| | - David A D Parry
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand. .,Riddet Institute, Massey University, Palmerston North, New Zealand.
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Structural Transition of Trichocyte Keratin Intermediate Filaments During Development in the Hair Follicle. Subcell Biochem 2017; 82:131-149. [PMID: 28101861 DOI: 10.1007/978-3-319-49674-0_5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The intermediate filaments (IF) in trichocyte (hard α-) keratin are unique amongst the various classes of IF in having not one but two topologically-distinct structures. The first is formed at an early stage of hair development in a reducing environment within the cells in the lower part of the follicle. The second structure occurs at a later stage of hair development in the upper part of the follicle, where there is a transition to an oxidizing environment. Crosslinking studies reveal that molecular slippage occurs within the IF upon oxidation and that this results in many cysteine residues lying in near axial alignment, thereby facilitating disulphide bond formation. The disulphide bonds so formed stabilize the assembly of IF molecules and convert the keratin fibre into a tough, resilient and insoluble structure suitable for its function in vivo as a thermo-regulator and a protector of the animal against its external environment.
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The Molecular Architecture for the Intermediate Filaments of Hard α-Keratin Based on the Superlattice Data Obtained from a Study of Mammals Using Synchrotron Fibre Diffraction. Biochem Res Int 2011; 2011:198325. [PMID: 22028970 PMCID: PMC3199101 DOI: 10.1155/2011/198325] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/23/2011] [Accepted: 08/23/2011] [Indexed: 11/21/2022] Open
Abstract
High- and low-angle X-ray diffraction studies of hard α-keratin have been studied, and various models have been proposed over the last 70 years. Most of these studies have been confined to one or two forms of alpha keratin. This high- and low-angle synchrotron fibre diffraction study extends the study to cover all available data for all known forms of hard α-keratin including hairs, fingernails, hooves, horn, and quills from mammals, marsupials, and a monotreme, and it confirms that the model proposed is universally acceptable for all mammals. A complete Bragg analysis of the meridional diffraction patterns, including multiple-time exposures to verify any weak reflections, verified the existence of a superlattice consisting of two infinite lattices and three finite lattices. An analysis of the equatorial patterns establishes the radii of the oligomeric levels of dimers, tetramers, and intermediate filaments (IFs) together with the centre to centre distance for the IFs, thus confirming the proposed helices within helices molecular architecture for hard α-keratin. The results verify that the structure proposed by Feughelman and James meets the criteria for a valid α-keratin structure.
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Smith TA, Parry DA. Three-dimensional modelling of interchain sequence similarities and differences in the coiled-coil segments of keratin intermediate filament heterodimers highlight features important in assembly. J Struct Biol 2008; 162:139-51. [DOI: 10.1016/j.jsb.2007.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Revised: 11/05/2007] [Accepted: 11/06/2007] [Indexed: 10/22/2022]
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Fraser RDB, Parry DAD. The three-dimensional structure of trichocyte (hard alpha-) keratin intermediate filaments: the nature of the repeating unit. J Struct Biol 2006; 155:375-8. [PMID: 16890455 DOI: 10.1016/j.jsb.2005.12.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 12/01/2005] [Indexed: 11/19/2022]
Abstract
Recently, the spatial distribution of the crosslinks induced between lysine residues in trichocyte (alpha-) keratin intermediate filaments (IF) using disulfosuccinimidyl tartrate was analyzed in detail and the results used to provide information about the three-dimensional structure of the IF [Fraser, R.D.B., Parry, D.A.D., 2005. The three-dimensional structure of trichocyte (hard alpha-) keratin intermediate filaments: features of the molecular packing deduced from the sites of induced crosslinks. J. Struct. Biol. 151, 171-181.] The presence of small amounts of 0--> +/-4 crosslinkages between molecular strands four distant in the network implied that the three-dimensional network of interacting molecules must be deeply puckered, but no specific suggestions were made about the nature of the puckering. Whilst it was recognized that there may be more than one type of molecular environment in the structural repeat the initial analysis was confined to the simplest case in which all molecules had the same environment, that is to say the asymmetric unit comprised a single molecule. Further studies reported here suggest that it is likely that the asymmetric unit consists of at least two and possibly as many as four molecules and the implications of this for modeling the structure of trichocyte IF are discussed.
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Fraser RDB, Steinert PM, Parry DAD. Structural changes in trichocyte keratin intermediate filaments during keratinization. J Struct Biol 2003; 142:266-71. [PMID: 12713954 DOI: 10.1016/s1047-8477(02)00636-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The so-called hard alpha-keratins, such as quill and hair, have a composite structure in which intermediate filaments (IF) are embedded in a sulfur-rich matrix. Recent studies of these trichocyte keratin IF have revealed that substantial changes in the molecular architecture take place when oxidation of the cysteine residues occurs as part of the terminal differentiation/keratinization process. Recent cryoelectron microscope studies suggest that the IF has a tubular structure prior to keratinization, but transmission electron micrographs of thin sections of fully keratinized fibers exhibit a "ring-core" structure. In the present contribution we develop a generic model for the IF in the reduced state based on cross-linking studies and discuss two possibilities for the way in which this structure may be modified during the keratinization process.
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Affiliation(s)
- R D Bruce Fraser
- Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
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Watts NR, Jones LN, Cheng N, Wall JS, Parry DAD, Steven AC. Cryo-electron microscopy of trichocyte (hard alpha-keratin) intermediate filaments reveals a low-density core. J Struct Biol 2002; 137:109-18. [PMID: 12064938 DOI: 10.1006/jsbi.2002.4469] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Trichocyte intermediate filaments (IF) are the principal components of epidermal appendages such as hair and nail. Based on studies by a variety of techniques, it has been inferred that trichocyte IF are structurally similar to other kinds of IF. However, some basic structural attributes have yet to be established: in particular, it has remained unclear whether IF are hollow. We have examined trichocyte IF isolated from rat vibrissae and human hair follicles by electron microscopy. Scanning transmission electron microscopy of freeze-dried specimens yielded mass-per-unit-length values of approximately 32 kDa/nm, with the human preparations also containing filaments at half this density, corresponding to two rather than four protofibrils. Radial density profiles calculated from cryo-electron micrographs of vitrified specimens preserved in a near-native state revealed a low-density region of approximately 3 nm diameter around the filament axis. A minor species of filament with the same internal structure was surface-decorated with material arranged with a helical pitch length of 9.3 nm. These filaments appear to represent IF coated with associated proteins-perhaps, "high-sulfur" proteins-readied for incorporation into the filament-matrix biocomposite of the mature hair.
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Affiliation(s)
- Norman R Watts
- Laboratory of Structural Biology Research, National Institutes of Health, Bethesda, Maryland 20892-8025, USA
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11
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Wang H, Parry DA, Jones LN, Idler WW, Marekov LN, Steinert PM. In vitro assembly and structure of trichocyte keratin intermediate filaments: a novel role for stabilization by disulfide bonding. J Cell Biol 2000; 151:1459-68. [PMID: 11134075 PMCID: PMC2150680 DOI: 10.1083/jcb.151.7.1459] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intermediate filaments (IF) have been recognized as ubiquitous components of the cytoskeletons of eukaryotic cells for 25 yr. Historically, the first IF proteins to be characterized were those from wool in the 1960s, when they were defined as low sulfur keratins derived from "microfibrils." These proteins are now known as the type Ia/type IIa trichocyte keratins that constitute keratin IF of several hardened epithelial cell types. However, to date, of the entire class of >40 IF proteins, the trichocyte keratins remain the only ones for which efficient in vitro assembly remains unavailable. In this paper, we describe the assembly of expressed mouse type Ia and type IIa trichocyte keratins into IF in high yield. In cross-linking experiments, we document that the alignments of molecules within reduced trichocyte IF are the same as in type Ib/IIb cytokeratins. However, when oxidized in vitro, several intermolecular disulfide bonds form and the molecular alignments rearrange into the pattern shown earlier by x-ray diffraction analyses of intact wool. We suggest the realignments occur because the disulfide bonds confer substantially increased stability to trichocyte keratin IF. Our data suggest a novel role for disulfide bond cross linking in stabilization of these IF and the tissues containing them.
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Affiliation(s)
- He Wang
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - David A.D. Parry
- Institute of Fundamental Sciences, Massey University, Palmerston North 5301, New Zealand
| | - Leslie N. Jones
- Commonwealth Scientific and Industrial Research Organisation, Division of Wool Technology, Belmont, Victoria 3216, Australia
| | - William W. Idler
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Lyuben N. Marekov
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Peter M. Steinert
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Busson B, Briki F, Doucet J. Side-chains configurations in coiled coils revealed by the 5.15-A meridional reflection on hard alpha-keratin X-ray diffraction patterns. J Struct Biol 1999; 125:1-10. [PMID: 10196111 DOI: 10.1006/jsbi.1999.4082] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The origin of the 5.15-A meridional reflection on hard alpha-keratin X-ray diffraction patterns is discussed in terms of side-chains conformations. We show it to reveal specific configurations of the side chains which are common to all two-stranded alpha-helical coiled coils. Combining literature data on crystallised coiled coil pieces and molecular dynamics results with our X-ray diffraction pattern simulations, we propose rules for the attribution of chi1 torsion angles for coiled coils involved in fibres whose structure cannot be resolved at atomic resolution: in a (a b c d e f g) heptad repeat, a and d residues, respectively, adopt mean t and g+ configurations, whereas statistical rules are given for the other residues.
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Affiliation(s)
- B Busson
- LURE, Bât 209-D, Université Paris-Sud, Orsay cedex, F-91898, France
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13
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Jones LN, Simon M, Watts NR, Booy FP, Steven AC, Parry DA. Intermediate filament structure: hard alpha-keratin. Biophys Chem 1997; 68:83-93. [PMID: 9468612 DOI: 10.1016/s0301-4622(97)00013-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Structurally there are four classes of intermediate filaments (IF) with distinct but closely related axial organisations. One of these, hard alpha-keratin IF, has been studied to clarify several apparently exceptional features which include the number of molecules in the IF cross-section and the mode by which the axial organisation of its constituent molecules is stabilised. Using the dark-field mode of the STEM at the Brookhaven National Laboratory (USA) mass measurements were obtained from unstained IF isolated from hair keratin. The data thus obtained show that the number of chains in cross-section is about 30 (+/-3: standard deviation) and is very similar to the numbers determined in previous STEM experiments for the dominant filament type in other classes of IF (about 32). Furthermore, re-analysis of the low-angle equatorial X-ray diffraction pattern reveals, in contrast to earlier work, solutions that are compatible with the number of chains in cross-section indicated by the STEM data. The absence of the head-to-tail overlap between parallel molecules characteristic of most of IF may be compensated in hard alpha-keratin by a network of intermolecular disulfide bonds. It is concluded that native IF of hard alpha-keratin and desmin/vimentin--and probably many other kinds of IF as well--contain about 32 chains in cross-section, and that the axial structures of these various kinds of IF differ in small but significant ways, while generally observing the same basic modes of aggregation.
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Affiliation(s)
- L N Jones
- CSIRO Division of Wool Technology, Belmont, Vic., Australia
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Parry DA. Protein chains in hair and epidermal keratin IF: structural features and spatial arrangements. EXS 1997; 78:177-207. [PMID: 8962493 DOI: 10.1007/978-3-0348-9223-0_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Over the past decade the progress made in characterising the structural hierarchy of both the hard and the epidermal keratin intermediate filaments has exceeded all expectations. The origin of much of this progress can be traced back to the quantity of amino acid sequence data that became available in the early/mid 1980s, and their interpretation in terms of a heterodimeric molecular structure. Subdomains were subsequently identified in both the rod and terminal domains, and now the roles of most of these have been determined in principle, if not yet fully in detail. TEM and STEM, together with very revealing crosslinking analyses have also allowed details to be determined of the mechanism by which molecules assemble into oligomers and oligomers into IF. It remains for the three-dimensional packing of keratin molecules in the IF to be elucidated, but even here progress is being made. A particularly exciting development over the last two or three years has been the establishment of the link between keratinopathies and single point nucleotide mutations in keratin genes. Furthermore, the clustering of mutation sites in regions involved in a key structural mode of molecular aggregation has provided, for the first time, an understanding of keratin diseases at the molecular level.
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Affiliation(s)
- D A Parry
- Department of Physics, Massey University, Palmerston North, New Zealand
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15
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Parry DA. Hard alpha-keratin IF: a structural model lacking a head-to-tail molecular overlap but having hybrid features characteristic of both epidermal keratin and vimentin IF. Proteins 1995; 22:267-72. [PMID: 7479699 DOI: 10.1002/prot.340220307] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In intermediate filaments (IF) both epidermal keratin and vimentin molecules have been shown to have an eight residue head-to-tail overlap between the rod domains of similarly directed molecules. In the case of the epidermal keratins this region has also been shown to have particular structural/functional significance since it represents a hot-spot for mutations in the four keratinopathies characterized to date. While there is good evidence that this head-to-tail overlap is present in IF containing Type III, IV, and V chains, as well as in the epidermal keratin IF (Ib/IIb), there are no data currently available for the hard alpha-keratin IF (Ia/IIa). Using a variety of data derived from X-ray diffraction and crosslinking studies, as well as theoretical modeling, it is now possible to demonstrate that the overlap region is not a feature of hard alpha-keratin IF. Indeed, it is shown that there is a nine residue gap between consecutive parallel molecules in the IF. An explanation for this observation is presented in terms of compensating disulfide bonds that occur both within the IF, and between the IF and the matrix in which the IF are embedded.
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Affiliation(s)
- D A Parry
- Department of Physics, Massey University, Palmerston North, New Zealand
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16
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Steinert PM, Marekov LN, Parry DA. Diversity of intermediate filament structure. Evidence that the alignment of coiled-coil molecules in vimentin is different from that in keratin intermediate filaments. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74552-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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17
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Steinert PM, Marekov LN, Parry DA. Conservation of the structure of keratin intermediate filaments: molecular mechanism by which different keratin molecules integrate into preexisting keratin intermediate filaments during differentiation. Biochemistry 1993; 32:10046-56. [PMID: 7691168 DOI: 10.1021/bi00089a021] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During development and differentiation, the intermediate filament component of the cytoskeleton of many cells and tissues is rebuilt by a dynamic exchange process in which one set of protein chains is replaced by another, without recourse to creation of a new network. One major example is the replacement of keratin 5/keratin 14 (K5/K14) keratin intermediate filaments (KIFs) by K1/K10 KIFs during terminal differentiation in the epidermis. The present work was undertaken to explore how this may occur. We have induced lysine-lysine cross-links with disulfosuccinimidyl tartrate in K5/K14 KIFs in order to determine the axial dimensions and relative axial alignments of the K5/K14 molecules. Many of the cross-links induced in subfilamentous oligomers containing one, two, or three molecules were also found in the intact KIF, indicating that the body of data thus generated provides physiologically relevant information on the structural organization in the KIF. A least-squares analysis using as data the positions of lysine residues involved in 23 induced cross-links has allowed the axial alignments of the various coiled-coil segments in the rod domain to be determined. Three modes of antiparallel alignment of two neighboring molecules were found: A11 (staggered by -16.7 nm), A22 (staggered by 28.8 nm), and A12 (almost in register; staggered by only 0.3 nm). Since the axial repeat length is about 1 nm less than the molecular length, the data require a fourth mode of molecule alignment, termed ACN, in which similarly directed molecules are overlapped by the equivalent of about 5-10 residues.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P M Steinert
- Skin Biology Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
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18
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Marshall RC, Orwin DF, Gillespie JM. Structure and biochemistry of mammalian hard keratin. ELECTRON MICROSCOPY REVIEWS 1991; 4:47-83. [PMID: 1714783 DOI: 10.1016/0892-0354(91)90016-6] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this review, the structure and biological formation of hard alpha-keratin are drawn together. The hard keratins comprising wool, hairs, quills, hooves, horns, nails and baleen contain partly alpha-helical polypeptides which show homology with epidermal polypeptides only in the helical regions. These polypeptides (about 32 chains) are organized into intermediate filaments (IFs) of 7.5 nm diameter which are embedded in variable amounts of a matrix of non-helical cystine-rich proteins and glycine-tyrosine-rich proteins. The total number of proteins may exceed 100. In addition keratins contain a variety of lipid components. Wool and hair are produced in follicles in a multistep procedure. In the lower levels of the follicle, IFs without associated matrix are found. Subsequently matrix proteins are laid down between the IFs and further synthesis takes place concurrently. Finally the proteins are insolubilized by the oxidative formation of disulphide bonds. Keratinized fibres shows considerable complexity and diversity in the structural arrangement of IFs and matrix within cortical cells. Typically the IFs show hexagonal packing or give a whorl-like appearance in cross-section.
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Affiliation(s)
- R C Marshall
- CSIRO Division of Wool Technology, Parkville, Victoria, Australia
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19
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Abstract
A recently-proposed model for the distribution of scattering material on the surface lattice of alpha-keratin intermediate filaments in dry porcupine quill is examined in detail. It is shown that, while retaining the basic form of the model (namely a dislocated helix with finite lattice spacing of 198.2 A), alternative meridonal distributions of scattering material within the finite lattice unit cell can be obtained which are consistent with the low-angle meridional X-ray pattern. The Gaussian shape function used to demonstrate the finite lattice in the model is questioned. The meridional diffraction pattern from hydrated porcupine quill is also examined and, apart from the intense fifth order reflection, can be modelled by distortion of the dry species scattering material distribution.
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Affiliation(s)
- M C Lawrence
- CSIRO Division of Biotechnology, Parkville, Victoria Australia
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20
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Stewart M, Quinlan RA, Moir RD. Molecular interactions in paracrystals of a fragment corresponding to the alpha-helical coiled-coil rod portion of glial fibrillary acidic protein: evidence for an antiparallel packing of molecules and polymorphism related to intermediate filament structure. J Cell Biol 1989; 109:225-34. [PMID: 2745549 PMCID: PMC2115473 DOI: 10.1083/jcb.109.1.225] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We have expressed in Escherichia coli a fragment of c-DNA that broadly corresponds to the alpha-helical coiled-coil rod section of glial fibrillary acidic protein (GFAP) and have used the resultant protein to prepare paracrystals in which molecular interactions can be investigated. An engineered fragment of mouse GFAP c-DNA was inserted into a modified version of the E. coli expression vector pLcII, from which large quantities of a lambda cII-GFAP rod fusion protein were prepared. A protein fragment corresponding to the GFAP rod was then obtained by proteolysis with thrombin. Paracrystals of this material were produced using divalent cations (Mg, Ca, Ba) in the presence of a chaotrophic agent such as thiocyanate. These paracrystals showed a number of polymorphic patterns that were based on a fundamental pattern that had dyad symmetry and an axial repeat of 57 nm. Analysis of both positive and negative staining patterns showed that this fundamental pattern was consistent with a unit cell containing two 48-nm-long molecules in an antiparallel arrangement with their NH2 termini overlapping by approximately 34 nm. More complicated patterns were produced by stacking the fundamental pattern with staggers of approximately 1/5, 2/5, and 1/2 the axial repeat. The molecular packing the unit cell was consistent with a range of solution studies on intermediate filaments that have indicated that a molecular dimer (i.e., a tetramer containing four chains or two coiled-coil molecules) is an intermediate in filament assembly. Moreover, these paracrystals allow the molecular interactions involved in the tetramer to be investigated in some detail.
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Affiliation(s)
- M Stewart
- Medical Research Council Laboratory of Molecular Biology, Cambridge, England
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Conway JF, Parry DA. Intermediate filament structure: 3. Analysis of sequence homologies. Int J Biol Macromol 1988. [DOI: 10.1016/0141-8130(88)90015-3] [Citation(s) in RCA: 131] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Previous x-ray diffraction studies on the alpha-keratins of hair and wool have revealed that the intermediate filaments (IF) have a helical structure rendered imperfect by a precisely defined dislocation. It has also been possible to deduce a surface lattice for the IF and to determine the number of IF molecules associated with each lattice point. In this work this information is combined with data on the ionic interactions between the coiled-coil rope segments of the IF molecules to provide a plausible model for the pattern of interactions that stabilize the framework of the IF in the "hard" alpha-keratins. Similar interaction studies of the proteins from the IF in the so-called "soft" alpha-keratin from the stratum corneum layer of the skin suggest that they are likely to have an essentially similar pattern.
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