The Sequence of a Gastropod Hemocyanin (HtH1 from Haliotis tuberculata)

Tello

General and Comparative Endocrinology

et al. 2008

105

Successful reproduction in vertebrates depends upon the actions of gonadotropin-releasing hormone (GnRH). Despite the wide presence of GnRH in Phylum Chordata, GnRH has not been isolated in protostomes other than the common octopus. To provide information on the evolution of this critical hormone, we isolated the full-length cDNA of a GnRH-like molecule from the central nervous system of a gastropod mollusk, the sea hare Aplysia californica. The open reading frame of this cDNA encodes a protein of 147 amino acids. The molecular architecture of the deduced protein is highly homologous to that reported for the prepro-octopus GnRH (oct-GnRH) and consists of a putative signal peptide, a GnRH dodecapeptide, a downstream processing site, and a GnRH-associated peptide (GAP). The deduced amino acid sequence of the Aplysia GnRH (ap-GnRH) is QNYHFSNGWYAG and differs from oct-GnRH by only two amino acids. The transcript for ap-GnRH is widely expressed in the central nervous system (CNS), the ovotestis, and the atrial gland, an exocrine gland. Immunocytochemistry (ICC) using an antiserum against oct-GnRH detected immunoreactive neurons in all CNS ganglia examined, and the staining was abolished by the preadsorption of the antiserum with synthetic ap-GnRH. In sum, ap-GnRH sequence is the first gastropod GnRH-like molecule to be elucidated. Further, it represents one of the only two GnRH-like molecules found outside Phylum Chordata. These data refute the possibility that oct-GnRH arose singly in cephalopods by convergent evolution and provide valuable support for an ancient origin of GnRH during metazoan evolution.

Section: Discussionmentioning

confidence: 99%

Molecular cloning, expression pattern, and immunocytochemical localization of a gonadotropin-releasing hormone-like molecule in the gastropod mollusk, Aplysia californica

Tello

General and Comparative Endocrinology

et al. 2008

105

Proc. Natl. Acad. Sci. U.S.A.

“…Considering all of the available data, it seems likely that both tyrosinases and molluscan hemocyanins evolved from a polypeptide chain that contained the copper A and B regions (1,2,4,8,9). The highly regular placement of the linker introns with respect to each preceding FU exon points to a repetitive, simple process for generating the multifunctional unit structures of molluscan hemocyanins from such a primordial unit.…”

Section: Discussionmentioning

confidence: 99%

“…Each copper is liganded by three histidine residues, forming a copper A site and a copper B site in each FU (1)(2)(3)(4). Recently, we and our collaborators reported the sequence of the polypeptide subunit of the cephalopod mollusk Octopus dofleini (2), the 2.3-Å tertiary structure of the C-terminal FU of this subunit (3), the polypeptide subunit sequence of the gastropod mollusk Haliotis tuberculata (4), and a 12-Å reconstruction of the quaternary structure of this hemocyanin (5). The polypeptide chain of Octopus hemocyanin (OdH) was found to contain 2,896 aa residues, divided into seven FUs, denoted OdH-a to OdH-g (from N to C terminus).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Structures of two molluscan hemocyanin genes: Significance for gene evolution

Lieb

Altenhein

Markl

et al. 2001

Self Cite

We present here the description of genes coding for molluscan hemocyanins. Two distantly related mollusks, Haliotis tuberculata and Octopus dofleini, were studied. The typical architecture of a molluscan hemocyanin subunit, which is a string of seven or eight globular functional units (FUs, designated a to h, about 50 kDa each), is reflected by the gene organization: a series of eight structurally related coding regions in Haliotis, corresponding to FU-a to FU-h, with seven highly variable linker introns of 174 to 3,198 bp length (all in phase 1). In Octopus seven coding regions (FU-a to FU-g) are found, separated by phase 1 introns varying in length from 100 bp to 910 bp. Both genes exhibit typical signal (export) sequences, and in both cases these are interrupted by an additional intron. Each gene also contains an intron between signal peptide and FU-a and in the 3 untranslated region. Of special relevance for evolutionary considerations are introns interrupting those regions that encode a discrete functional unit. We found that five of the eight FUs in Haliotis each are encoded by a single exon, whereas FU-f, FU-g, and FU-a are encoded by two, three and four exons, respectively. Similarly, in Octopus four of the FUs each correspond to an uninterrupted exon, whereas FU-b, FU-e, and FU-f each contain a single intron. Although the positioning of the introns between FUs is highly conserved in the two mollusks, the introns within FUs show no relationship either in location nor phase. It is proposed that the introns between FUs were generated as the eight-unit polypeptide evolved from a monomeric precursor, and that the internal introns have been added later. A hypothesis for evolution of the ring-like quaternary structure of molluscan hemocyanins is presented.

“…Unlike all other FUs, FU-h has an additional C-terminal extension of approximately 100 amino acids, which marks the very end of the molluscan hemocyanin subunit polypeptide (21). The sequence of this extension could not be related to any other sequence or fold in the databases for a long time.…”

Section: Introductionmentioning

confidence: 99%

The refined structure of functional unit h of keyhole limpet hemocyanin (KLH1‐h) reveals disulfide bridges

et al. 2011

Self Cite

Hemocyanins are multimeric oxygen‐transport proteins in the hemolymph of many arthropods and mollusks. The overall molecular architecture of arthropod and molluscan hemocyanin is very different, although they possess a similar binuclear type 3 copper center to bind oxygen in a side‐on conformation. Gastropod hemocyanin is a 35 nm cylindrical didecamer (2 × 10‐mer) based on a 400 kDa subunit. The latter is subdivided into eight paralogous “functional units” (FU‐a to FU‐h), each with an active site. FU‐a to FU‐f contribute to the cylinder wall, whereas FU‐g and FU‐h form the internal collar complex. Atomic structures of FU‐e and FU‐g, and a 9 Å cryoEM structure of the 8 MDa didecamer are available. Recently, the structure of keyhole limpet hemocyanin FU‐h (KLH1‐h) was presented as a Cα‐trace at 4 Å resolution. Unlike the other seven FU types, FU‐h contains an additional C‐terminal domain with a cupredoxin‐like fold. Because of the resolution limit of 4 Å, in some loops, the course of the protein backbone could not be established with high certainty yet. Here, we present a refined atomic structure of FU‐h (KLH1‐h) obtained from low‐resolution refinement, which unambiguously establishes the course of the polypeptide backbone and reveals the disulfide bridges as well as the orientation of bulky amino acids. © 2011 IUBMB IUBMB Life, 63(3): 183–187, 2011