The occurrence of proctolin (Arg-Tyr-Leu-Pro-Thr) in crab neurohemal pericardial organs (POs) has been demonstrated by isolation of the pentapeptide by HPLC and manual microsequencing according to the DABITC-PITC double coupling technique. From one pair of POs approximately 5.4 pmol were obtained (= 45 pmol/mg protein). Immunocytochemically, an extensive system of positive structures was found in both whole mount preparations and semithin sections, consisting of numerous varicose fibres of varying diameter and many knoblike neurosecretory terminals abutting upon the epineurium of the PO trunks. The relatively high concentration in the POs as well as the pattern of proctolin-positive fibres and terminals clearly suggest a neurohormonal role of the pentapeptide in decapod crustaceans.

Amino Acid Sequence↗

PubMedDate not supplied

Distribution of a novel cardioactive neuropeptide (CCAP) in the nervous system of the shore crab Carcinus maenas.

A radioimmunoassay (RIA) for the recently discovered crustacean cardioactive peptide (CCAP) has been developed and used to determine contents of CCAP in different parts of the nervous system of the shore crab Carcinus maenas. Immunoreactive material was detected throughout the nervous system. In contrast to the main ganglia which contained low levels of approximately 1.4 pmol CCAP/mg protein (brain and thoracic ganglion), a high concentration was found in a neurohemal structure, the pericardial organs (PO) (868 pmol/mg protein). A predominantly neurohormonal role of CCAP thus suggested is further supported by in vitro release studies. Incubation of POs in high (K+) saline showed that CCAP is secretable in considerable amounts by a Ca++-dependent release mechanism.

Animals↗

PubMedDate not supplied

Amino acid sequence of crustacean hyperglycemic hormone (CHH) from the crayfish, Orconectes limosus: emergence of a novel neuropeptide family.

The primary structure of the major form of CHH from sinus glands of the crayfish, Orconectes limosus, was determined by manual Edman microsequencing. It is a 72-residue peptide with a calculated Mr of 8400 Da. In the number of residues, it is identical to the CHH of Carcinus maenas and very similar to MIH (moult inhibiting hormone) of Homarus americanus. All three peptides have pGlu as N-terminus in common, and Val-NH2 is the C-terminal residue in Orconectes and Carcinus CHH. Six Cys residues occupy identical position in the three peptides. There is a 61% sequence identity with Carcinus CHH, and an 81% identity with Homarus MIH.

Amino Acid Sequence↗

PubMedDate not supplied

Isolation and amino acid sequence of crustacean hyperglycemic hormone precursor-related peptides.

The crustacean hyperglycemic hormone (CHH) is synthesized as part of a larger preprohormone in which the sequence of CHH is N-terminally flanked by a peptide for which the name CPRP (CHH precursor-related peptide) is proposed. Both CHH and CPRP are present in the sinus gland, the neurohemal organ of neurosecretory cells located in the eyestalk of decapod crustaceans. This paper describes the isolation and sequence analysis of CPRPs isolated from sinus glands of the crab Carcinus maenas, the crayfish Orconectes limosus and the lobster Homarus americanus. The published sequence of "peptide H" isolated from the land crab, Cardisoma carnifex, has now been recognized as a CPRP in this species. Sequence comparison reveals a high level of identity for the N-terminal region (residues 1-13) between all four peptides, while identity in the C-terminal domain is high between lobster and crayfish CPRP on the one hand, and between both crab species on the other. Conserved N-terminal residues include a putative monobasic processing site at position 11, which suggests that CPRP may be a biosynthetic intermediate from which a potentially bioactive decapeptide can be derived.

Amino Acid Sequence↗