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R Z Zhang

Publications and source records attributed to R Z Zhang.

At least 37 records · Page 2Linked to original sources
PubMed1994

Fibulin-2 (FBLN2): human cDNA sequence, mRNA expression, and mapping of the gene on human and mouse chromosomes.

Fibulin-2 is a new extracellular matrix protein that we recently identified by characterizing mouse cDNA clones. Fibulin-2 mRNA is prominently expressed in mouse heart tissue and is present in low amounts in other tissues. In this study, we isolated and sequenced a 4.1-kb human fibulin-2 cDNA, which encoded a mature protein of 1157 amino acids preceded by a 27-residue signal sequence. The predicted polypeptide contains three consecutive anaphylatoxin-related segments (domain I) in its central region followed by 10 EGF-like repeats (domain II), 9 of which have a consensus sequence for calcium binding. The 408-residue N-terminal region consists of two separate subdomains, a cysteine-rich segment of 150 residues (Na subdomain) and a cysteine-free segment with a stretch of acidic amino acids (Nb subdomain). The 115-residue C-terminal segment (domain III) is similar to the C variant of fibulin-1. The amino acid sequences of the human and mouse fibulin-2 share approximately 90% identity in domains Na, I, II, and III but only 62% identity in domain Nb. The human cDNA lacks an EGF-like repeat, which is alternatively spliced in the mouse cDNA clones, and a potential cell-binding Arg-Gly-Asp sequence found in the Nb domain of the mouse counterpart. Northern blot analysis of mRNA from various human tissues reveals an abundant 4.5-kb transcript in heart, placenta, and ovary tissue. The expression pattern differs from that of fibulin-1. The fibulin-2 gene was localized by in situ hybridization to the p24-p25 region of human chromosome 3 and to the band D-E of mouse chromosome 6.

Amino Acid Sequence↗
PubMed1994

The fibulin-1 gene (FBLN1) is located on human chromosome 22 and on mouse chromosome 15.

Fibulin-1 is a calcium-binding glycoprotein present in the extracellular matrix and in the serum. The gene coding for fibulin-1 (FBLN1) was located by in situ hybridization of 3H-labeled cDNA probes to human and mouse metaphase chromosomes. The gene was assigned to the q13.2-q13.3 region of human chromosome 22 and to the E-F band of mouse chromosome 15. This finding extends the evolutionary conservation between human chromosome 22 and mouse chromosome 15.

Animals↗
PubMed1994

Recombinant expression and structural and binding properties of alpha 1(VI) and alpha 2(VI) chains of human collagen type VI.

Full-length alpha 1(VI) and alpha 2(VI) cDNAs in an eukaryotic expression vector were used to obtain stably transfected human kidney cell clones and to purify these collagen-VI chains in substantial quantities from the culture medium. Both chains appeared mainly as monomers together with some dimers that were disulfide linked through their C-terminal globular domains. Despite sufficient hydroxylation of proline and lysine residues, the chains did not form a triple-helix, as shown by electronmicroscopy, CD spectra and pepsin sensitivity. Digestion of the chains with bacterial collagenase released the N-terminal and C-terminal globular domains, which were identified by their size and partial sequences. They showed a substantial content of alpha-helical conformation and a distinct globular structure after rotary shadowing. Antibodies could be raised that distinguished between the two chains and reacted with the globular domains. The alpha 2(VI) but not the alpha 1(VI) chain showed binding to a heparan sulfate proteoglycan (perlecan), fibronectin and pepsin-solubilized collagen VI. Purified globular domains did not bind these ligands indicating the localization of binding sites within the triple-helical domain. Both chains showed a distinct affinity for heparin but failed to bind to various collagen types.

Amino Acid Sequence↗
PubMed1993

Sequence of extracellular mouse protein BM-90/fibulin and its calcium-dependent binding to other basement-membrane ligands.

Partial sequence comparisons have recently indicated that two extracellular components, fibulin from human placenta and BM-90 from a basement-membrane-producing mouse tumor, are either identical or closely related proteins. In this study, a complete sequence analysis of mouse BM-90 cDNA showed a 539-residue N-terminal core structure (domains I and II), which was 85% identical with the same core structure of human fibulin. A 137-residue C-terminal sequence (domain III) was unique for BM-90 and could also be identified by Edman degradation. This suggested a novel splice product, variant D, which is characteristic for the mouse tumor. A second 117-residue C-terminal sequence (domain III) was identified in additional mouse cDNA clones and showed 91% identity with the region specific for variant C of fibulin. Northern blots using mouse cells demonstrated two mRNA species, 2.7 kb and 2.3 kb, which encoded the variants D and C, respectively. The sequence of BM-90/fibulin indicates the presence of nine epidermal-growth-factor-like repeats in the core domain-II structure, eight of which contain consensus motifs for calcium binding. This binding is apparently important for the interaction of BM-90 with laminin and nidogen and for some weaker interactions with collagen IV. Further binding of BM-90 was demonstrated to fibronectin and BM-90 itself, but did not depend on calcium. Major binding sites for BM-90 were identified at a C-terminal segment of laminin A chain and at the N-terminus of nidogen. The broad interaction repertoire of BM-90 is comparable to that of nidogen and both proteins may have similar roles as connecting elements in the extracellular matrix.

Alternative Splicing↗
PubMed1993

Cloning and sequence analysis of cDNAs encoding the alpha 1, alpha 2 and alpha 3 chains of mouse collagen VI.

cDNA clones encoding the alpha 1, alpha 2 and alpha 3 chains of mouse collagen VI have been isolated by screening cDNA libraries with the corresponding human probes. The composite cDNAs for the alpha 1, alpha 2, and alpha 3 chains are 2.5, 1.6 and 2.9 kb in size respectively. The alpha 1 and alpha 2 cDNAs encode the C-terminal portions of the chains as well as the entire 3'-untranslated regions, while the alpha 3 cDNAs encode a central segment of 959 amino acids flanking the triple-helical domain. The deduced amino acid sequences share 86-88% identity with the human counterparts and 67-73% identity with the chicken equivalents. Alignment of the deduced amino acid sequences of mouse, human and chicken collagens reveal that the key features of the protein, including the cysteine residues, imperfections in the Gly-Xaa-Xaa regions, Arg-Gly-Asp sequences and potential N-glycosylation sites, are mostly conserved.

Amino Acid Sequence↗
PubMed1993

Structure and expression of fibulin-2, a novel extracellular matrix protein with multiple EGF-like repeats and consensus motifs for calcium binding.

A new protein, fibulin-2, was predicted from sequence analysis of cDNA clones obtained from a mouse fibroblast library. This protein consists of a 1195-residue polypeptide preceded by a 26-residue signal peptide. The COOH-terminal region of 787 amino acids contained three anaphylatoxin-related segments (domain I), 11 EGF-like repeats (domain II), 10 of which had a consensus motif for calcium-binding, and a 115-residue globular domain III. Except for two additional EGF-like repeats, this COOH-terminal region showed 43% sequence identity with the previously described fibulin-1 (BM-90). The NH2-terminal 408 residues, unique to fibulin-2, showed no sequence homology to other known proteins and presumably form two additional domains that differ in their cysteine content. Recombinant fibulin-2 was produced and secreted by human cell clones as a disulfide-bonded trimer. Rotary shadowing visualized the protein as three 40-45 nm long rods which are connected at one end in a globe-like structure. No significant immunological cross-reaction could be detected between fibulin-1 and fibulin-2. Production of the fibulin-2 was demonstrated by Northern blots and radioimmunoassay in fibroblasts but not in several tumor cell lines. Together with the observation that the serum level of fibulin-2 is 1,000-fold lower than that of fibulin-1, the data indicate that these two isoforms are not always coordinately expressed. This is also suggested by Northern blots of tissue mRNAs and by immunofluorescence localizations using mouse tissues. The latter studies also demonstrated an extracellular localization for fibulin-2 in basement membranes and other connective tissue compartments.

Amino Acid Sequence↗
PubMed1993

Hyperglycemic glucose concentrations up-regulate the expression of type VI collagen in vitro. Relevance to alterations of peripheral nerves in diabetes mellitus.

Electron microscopy of peripheral nerves obtained from two diabetic patients revealed large deposits of microfibrils and the presence of Luse bodies in the vicinity of perineurial cells. Microfibrils were found to accumulate also in the sciatic nerves of diabetic BB rats; these microfibrillar deposits were shown to contain type VI collagen by immunoelectron microscopy. Connective tissue cells cultured from rat sciatic nerves were exposed to high glucose concentrations. High glucose concentrations up-regulated the mRNA steady-state levels of alpha 1(VI), alpha 2(VI), and alpha 3(VI) chains of type VI collagen and caused accumulation of type VI collagen-containing fibrils in the cultures. Immunostaining and in situ hybridizations demonstrated that perineurial cells, Schwann cells, and fibroblasts expressed type VI collagen at the mRNA and protein levels. The results suggest that the turnover and supramolecular assembly of type VI collagen are perturbed in diabetic nerves and that glucose per se increases the expression of type VI collagen in vitro.

Adolescent↗
PubMed1992

Cloning and chromosomal location of human alpha 1(XVI) collagen.

We have characterized cDNA clones that encode a newly discovered collagenous polypeptide. A 4-kilobase (kb) cDNA clone was initially isolated by screening a human fibroblast cDNA library with a probe encoding the collagenous domain of the human alpha 3(VI) collagen. Subsequent screening of another fibroblast cDNA library yielded overlapping clones having a total length of 5.4 kb, which contained an open reading frame of 1603 amino acids including a 21-amino acid signal peptide. The predicted polypeptide consists of 10 collagenous domains 15-422 amino acids long, which were interspersed with 11 noncollagenous (NC) domains. Except for a large N-terminal NC11 domain of 312 residues, most of the NC domains were short (11-39 residues) and cysteine-rich. The overall structural arrangement differed significantly from other known collagen chains. Further analysis indicated that the deduced polypeptide exhibited several structural features characteristically seen in members of the fibril-associated collagen, types IX, XII, and XIV. In addition, the cysteine-rich motifs in the NC domains resembled those found in the cuticle collagen of Caenorhabditis elegans. Northern blot analyses showed hybridization of the cDNA to a 5.5-kb mRNA in human fibroblasts and keratinocytes. The gene was localized by in situ hybridization to band p34-35 of human chromosome 1. The data clearly support the conclusion that the cDNA encodes a collagen chain that has not been previously described. We suggest that the cDNA clones encode the alpha 1 chain of type XVI collagen.

Amino Acid Sequence↗
PubMed1992

The large non-collagenous domain (NC-1) of type VII collagen is amino-terminal and chimeric. Homology to cartilage matrix protein, the type III domains of fibronectin and the A domains of von Willebrand factor.

Type VII collagen, the major component of anchoring fibrils, consists of a central collagenous triple-helical segment flanked by non-collagenous domains, NC-1 and NC-2. In this study, we examined the domain organization of human type VII collagen through analysis of deduced amino acid sequences derived from cloned complementary and genomic DNAs, as compared to peptide segments derived from amniotic membrane type VII collagen. The results revealed that the peptide segments derived from the NC-1 domain of type VII collagen could be assigned to the 5' portion of the composite cDNA, indicating that NC-1 resides at the amino terminal end of the molecule. Several sub-domains with homology to adhesive molecules were also identified within NC-1. These protein domains may confer adhesive properties to NC-1, thereby facilitating the binding of type VII collagen to the lamina densa in the cutaneous basement membrane and the anchoring plaques within the dermis.

Amino Acid Sequence↗
PubMed1991

The exon organization of the triple-helical coding regions of the human alpha 1(VI) and alpha 2(VI) collagen genes is highly similar.

The alpha 1(VI) and alpha 2(VI) chains, two of the three constituent chains of type VI collagen, are highly similar in size and domain structure. They are encoded by single-copy genes residing in close proximity on human chromosome 21. To study the evolution of the type VI collagen genes, we have isolated and characterized genomic clones coding for the triple-helical domains of the human alpha 1(VI) and alpha 2(VI) chains, which consist of 336 and 335 amino acid residues, respectively. Nucleotide sequencing indicates that, in both genes, the exons are multiples of 9 bp in length (including 27, 36, 45, 54, 63, and 90 bp) except for those encoding for regions with triple-helical interruptions. In addition, the introns are positioned between complete codons. The most predominant exon size is 63 bp, instead of 54 bp as seen in the fibrillar collagen genes. Of particular interest is the finding that the exon structures of the alpha 1(VI) and alpha 2(VI) genes are almost identical. A significant deviation is that a segment of 30 amino acid residues is encoded by two exons of 54 and 36 bp in the alpha 1(VI) gene, but by a single exon of 90 bp in the alpha 2(VI) gene. The exon arrangement therefore provides further evidence that the two genes have evolved from tandem gene duplication. Furthermore, comparison with the previously reported gene structure of the chick alpha 2(VI) chain indicates that the exon structure for the triple-helical domain of the alpha 2(VI) collagen is strictly conserved between human and chicken.

Amino Acid Sequence↗
PubMed1990

Mosaic structure of globular domains in the human type VI collagen alpha 3 chain: similarity to von Willebrand factor, fibronectin, actin, salivary proteins and aprotinin type protease inhibitors.

Human collagen alpha 3(VI) chain mRNA (approximately 10 kb) was cloned and shown by sequence analysis to encode a 25 residue signal peptide, a large N-terminal globule (1804 residues), a central triple helical segment (336 residues) and a C-terminal globule (803 residues). Some of the sequence was confirmed by Edman degradation of peptides. The N-terminal globular segment consists of nine consecutive 200 residue repeats (N1 to N9) showing internal homology and also significant identity (17-25%) to the A domains of von Willebrand Factor and similar domains present in some other proteins. Deletions were found in the N3 and N9 domains of several cDNA clones suggesting variation of these structures by alternative splicing. The C-terminal globule starts immediately after the triple helical segment with two domains C1 (184 residues) and C2 (248 residues) being similar to the N domains. They are followed by a proline rich, repetitive segment C3 of 122 residues, with similarity to some salivary proteins, and domain C4 (89 residues), which is similar to the type III repeats present in fibronectin and tenascin. The most C-terminal domain C5 (70 residues) shows 40-50% identity to a variety of serine protease inhibitors of the Kunitz type. The whole sequence contains 29 cysteines which are mainly clustered in short segments connecting domains N1, C1, C2 and the triple helix, and in the inhibitor domain. Five putative Arg-Gly-Asp cell-binding sequences are exclusively localized in the triple helical segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗