HFP) of the Syrian golden hamster [206]. The
known mammalian pentraxins share 69 invariant
amino acids [270]. CRP and SAP can be easily
identified on the basis of their binding specificities: CRP shows specific affinity for phosphorylcholine and SAP for agarose. Both proteins
are found in a wide range of very different vertebrates, including the cartilaginous and the bony
fish; the CRP of the dogfish Mustelus canis is
even cross-reactive with that of the rabbit [210]. It
is noteworthy that CRP-like proteins have also
been detected in an invertebrate, the horseshoe
crab Limulus polyphemus. The CRP in this case
has a concentration of 1-5 mg/ml and is a constitutive, major component of the haemolymph; in
contrast to the vertebrate protein, it consists of
non-identical, 24-kDa subunits in a 2 X 6
arrangement. Three CRP genes from Limulus
have been sequenced. The encoded polypeptides
of 218 amino acids differ from each other by up to
10 % but agree to about 25 % with human CRP,
and even more so in two conserved regions.
Limulus possesses more than three CRP genes
compared with the one gene of man [191, 192].
5.5 Larval Haemolympb Proteins
of Insects
A type of haemolymph protein was discovered in
1969 in the fly Calliphora vicina (identical to
C. erythrocephala); this protein appears only in
older larvae and the pupa, and disappears again
during metamorphosis to the imago. Subsequently, similar proteins were demonstrated in
other dipterans, various lepidopterans, the bug
Rhodnius prolixus and the cockroach Blatta
orientalis [121, 128, 129, 207]. Their function is
apparently that of amino acid storage during the
periods of ecdysis and metamorphosis when there
is intensive metabolism but no nutrient intake.
Initially, these proteins were named according to
their source, e.g. calliphorin, lucilin, manducin
etc.; today, they are generally known as larval
haemolymph proteins (LHPs) or, in view of their
high aromatic amino acid content, as arylphorins.
LHPs are synthesized in the fat bodies of older
larvae and secreted into the haemolymph. In the
Lepidoptera, the arylphorin genes are also
expressed in other tissues, although at lower
levels than in the fat bodies [121, 165]. At the end
of the feeding phase, LHPs make up 60-80 % of
the total haemolymph proteins, i.e. up to 6 % of
larval fresh weight. During the migration phase
5.5 Larval Haemolymph Proteins of Insects
191
or shortly before pupation, the LHPs are taken
up again by the fat bodies and stored in 1.5- to
3.0-!.lm-Iarge granulae. The recovery of LHPs
into the fat bodies has been studied in Sarcophaga peregrina and Musca domestica. There is a
characteristic sequence in the house fly with a
maximum at larval migration. The LHPs from
Drosophila melanogaster and Rhynchosciara
americana can also be taken up by the fat bodies
of Musca, although that of R. americana in fact
shows no cross-reactivity with the Musca LHP.
The responsible membrane receptor therefore
appears to have no great specificity [121, 155].
LHPs disappear completely during the histolysis
that occurs in the pupa, but little is known in
detail about their degradation. It has been shown
in Calliphora vicina that the ubiquitin which is
present is not involved in the intracellular cleavage of calliphorin [146].
The biological functions of the LHPs are not
yet completely clear. It can be assumed that LHPs
provide amino acids for the synthesis of structural
and nutritional substances during metamorphosis, including the aromatic amino acids for the
sclerotization of the cuticle. However, arylphorins are also found intact in the sclerotized cuticle
of the fly Calliphora vicina and the butterfly Manduca sexta; the LHPs of Drosphila, Calliphora
and Manduca are polymerized in vitro under oxidizing conditions by sclerotizing substances such
as N-acetyldopamine and N-B-alanyldopamine.
Thus, the arylphorins appear to be structural
components of the sclerotized cuticle. The LHPs
also probably have other functions, e.g. as transport proteins for ecdysteron. A strain of Drosophila melanogaster which cannot make arylphorin
because of a genetic defect showed a 15-fold
reduction in fertility during a 2-year observation
period but there were no negative effects on survival [121].
The LHPs have a very unusual amino acid
spectrum with a total of 17-26 % phenylalanine
and tyrosine. Small amounts of carbohydrates
could be detected in all examined LHPs and in
some cases there was also a lipid component
[121, 145]. The structure of the N-glycosyl chain
has, as yet, only been analysed in the butterfly
M. sexta, where it turns out to be the typical
asparagine-bound oligosaccharide Man9GlcNAez
(see Fig. 13.17, p.491) [216,224]. The LHPs are
hexamers of 450-500 kDa with subunits of
72-83 kDa. Multiple LHPs are found in several
species and are referred to, for example, as LHPI, II, etc. In these cases, several types of subunit
have been detected which combine to form differ-
known mammalian pentraxins share 69 invariant
amino acids [270]. CRP and SAP can be easily
identified on the basis of their binding specificities: CRP shows specific affinity for phosphorylcholine and SAP for agarose. Both proteins
are found in a wide range of very different vertebrates, including the cartilaginous and the bony
fish; the CRP of the dogfish Mustelus canis is
even cross-reactive with that of the rabbit [210]. It
is noteworthy that CRP-like proteins have also
been detected in an invertebrate, the horseshoe
crab Limulus polyphemus. The CRP in this case
has a concentration of 1-5 mg/ml and is a constitutive, major component of the haemolymph; in
contrast to the vertebrate protein, it consists of
non-identical, 24-kDa subunits in a 2 X 6
arrangement. Three CRP genes from Limulus
have been sequenced. The encoded polypeptides
of 218 amino acids differ from each other by up to
10 % but agree to about 25 % with human CRP,
and even more so in two conserved regions.
Limulus possesses more than three CRP genes
compared with the one gene of man [191, 192].
5.5 Larval Haemolympb Proteins
of Insects
A type of haemolymph protein was discovered in
1969 in the fly Calliphora vicina (identical to
C. erythrocephala); this protein appears only in
older larvae and the pupa, and disappears again
during metamorphosis to the imago. Subsequently, similar proteins were demonstrated in
other dipterans, various lepidopterans, the bug
Rhodnius prolixus and the cockroach Blatta
orientalis [121, 128, 129, 207]. Their function is
apparently that of amino acid storage during the
periods of ecdysis and metamorphosis when there
is intensive metabolism but no nutrient intake.
Initially, these proteins were named according to
their source, e.g. calliphorin, lucilin, manducin
etc.; today, they are generally known as larval
haemolymph proteins (LHPs) or, in view of their
high aromatic amino acid content, as arylphorins.
LHPs are synthesized in the fat bodies of older
larvae and secreted into the haemolymph. In the
Lepidoptera, the arylphorin genes are also
expressed in other tissues, although at lower
levels than in the fat bodies [121, 165]. At the end
of the feeding phase, LHPs make up 60-80 % of
the total haemolymph proteins, i.e. up to 6 % of
larval fresh weight. During the migration phase
5.5 Larval Haemolymph Proteins of Insects
191
or shortly before pupation, the LHPs are taken
up again by the fat bodies and stored in 1.5- to
3.0-!.lm-Iarge granulae. The recovery of LHPs
into the fat bodies has been studied in Sarcophaga peregrina and Musca domestica. There is a
characteristic sequence in the house fly with a
maximum at larval migration. The LHPs from
Drosophila melanogaster and Rhynchosciara
americana can also be taken up by the fat bodies
of Musca, although that of R. americana in fact
shows no cross-reactivity with the Musca LHP.
The responsible membrane receptor therefore
appears to have no great specificity [121, 155].
LHPs disappear completely during the histolysis
that occurs in the pupa, but little is known in
detail about their degradation. It has been shown
in Calliphora vicina that the ubiquitin which is
present is not involved in the intracellular cleavage of calliphorin [146].
The biological functions of the LHPs are not
yet completely clear. It can be assumed that LHPs
provide amino acids for the synthesis of structural
and nutritional substances during metamorphosis, including the aromatic amino acids for the
sclerotization of the cuticle. However, arylphorins are also found intact in the sclerotized cuticle
of the fly Calliphora vicina and the butterfly Manduca sexta; the LHPs of Drosphila, Calliphora
and Manduca are polymerized in vitro under oxidizing conditions by sclerotizing substances such
as N-acetyldopamine and N-B-alanyldopamine.
Thus, the arylphorins appear to be structural
components of the sclerotized cuticle. The LHPs
also probably have other functions, e.g. as transport proteins for ecdysteron. A strain of Drosophila melanogaster which cannot make arylphorin
because of a genetic defect showed a 15-fold
reduction in fertility during a 2-year observation
period but there were no negative effects on survival [121].
The LHPs have a very unusual amino acid
spectrum with a total of 17-26 % phenylalanine
and tyrosine. Small amounts of carbohydrates
could be detected in all examined LHPs and in
some cases there was also a lipid component
[121, 145]. The structure of the N-glycosyl chain
has, as yet, only been analysed in the butterfly
M. sexta, where it turns out to be the typical
asparagine-bound oligosaccharide Man9GlcNAez
(see Fig. 13.17, p.491) [216,224]. The LHPs are
hexamers of 450-500 kDa with subunits of
72-83 kDa. Multiple LHPs are found in several
species and are referred to, for example, as LHPI, II, etc. In these cases, several types of subunit
have been detected which combine to form differ-