title: Molecular architecture of silk fibroin of Indian golden silkmoth, Antheraea assama.
abstract: The golden silk spun by Indian golden silkmoth Antheraea assama, is regarded for its shimmering golden luster, tenacity and value as biomaterial. This report describes the gene coding for golden silk H-fibroin (AaFhc), its expression, full-length sequence and structurally important motifs discerning the underlying genetic and biochemical factors responsible for its much sought-after properties. The coding region, with biased isocodons, encodes highly repetitious crystalline core, flanked by a pair of 5' and 3' non-repetitious ends. AaFhc mRNA expression is strictly territorial, confined to the posterior silk gland, encoding a protein of size 230 kDa, which makes homodimers making the elementary structural units of the fibrous core of the golden silk. Characteristic polyalanine repeats that make tight β-sheet crystals alternate with non-polyalanine repeats that make less orderly antiparallel β-sheets, β-turns and partial α-helices. Phylogenetic analysis of the conserved N-terminal amorphous motif and the comparative analysis of the crystalline region with other saturniid H-fibroins reveal that AaFhc has longer, numerous and relatively uniform repeat motifs with lower serine content that assume tighter β-crystals and denser packing, which are speculated to be responsible for its acclaimed properties of higher tensile strength and higher refractive index responsible for golden luster.
authors.affiliation: Centre of Excellence for Genetics and Genomics of Silkmoths, Laboratory of Molecular Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India.
authors.forename: Adarsh K
authors.initials: AK
authors.lastname: Gupta
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China.
authors.forename: Kazuei
authors.initials: K
authors.lastname: Mita
authors.affiliation: Centre of Excellence for Genetics and Genomics of Silkmoths, Laboratory of Molecular Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India.
authors.forename: Kallare P
authors.initials: KP
authors.lastname: Arunkumar
authors.affiliation: 1] Centre of Excellence for Genetics and Genomics of Silkmoths, Laboratory of Molecular Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India [2] Deceased.
authors.forename: Javaregowda
authors.initials: J
authors.lastname: Nagaraju
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001483:Base Sequence; D005349:Fibroins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005796:Genes; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009036:Moths / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D019476:Insect Proteins; D005349:Fibroins