What is IGF-1 LR3?
IGF-1 LR3, also known as Long Arg3 IGF-1, is a recombinant protein
analogue of human Insulin-Like Growth Factor-1 that has a molar
mass of 9,200 Daltons and is comprised of 83 amino acids. IGF-1 LR3
comprises the complete IGF-1 sequence, but with a 13 amino acid
extension on the B-Terminus domain and the substitution of an
Arginine for the Glutamic Acid at position 3. The LR3 analogue of
IGF-1 was created with the intent to drastically increase the
biological activity of the protein and IGF-LR3 is several times
more potent than rhIGF-1. This specific sequence alteration has
decreased the affinity of binding to the IGFBPs, which control the
biological actions of IGF-1 and prevent the protein from reaching
the IGF-1 receptors.
IGF-1 LR3 is an 83 amino acid analogue of human IGF-1 that has been
modified to include a 13 amino acid extension on its N-Terminus and
the substitution of an Arginine amino acid for Glutamine at
While IGF-1 LR3 is comprised of the the complete human IGF-1
sequence, these modifications have rendered the LR3 version to be
much more potent than IGF-1 in-vitro and in-vivo. The result of
these modifications is that IGF-1 LR3 does not bind as strongly to
the IGFBPs, which modify the biological actions of IGF-1.
Resultantly, IGF-1 LR3 binds to the type 1 IGF-1 receptor with
similar affinity to that of wild type IGF-1, but with higher
biological activity and has several advantages over recombinant
The supplementation of mammalian cell cultures with Long R3 IGF-1
at a much lower concentration results in more highly elevated
productivity than with standard concentrations of insulin and/or
standard IGF-1. IGF-1 LR3 is better able to stimulate the type 1
IGF receptor and thus induce a higher level of activation of
intracellular signaling, which is responsible for promoting cell
proliferation and the inhibition of apoptosis.
What is the Amino Acid Sequence of IGF-1 LR3?
The amino acid sequence (three letter) is
Receptor Grade vs Media Grade IGF-1 LR3
Genuine Receptor Grade LR3 IGF-I is a high quality research reagent
for use in studies on cell growth, IGF receptors and IGF binding
proteins and is more potent than rH IGF-1 and Media Grade IGF-1 LR3
both in vivo and in vitro due to the drastic increase in biological
activity (stronger affinity for binding with the IGF receptor) and
high-level purity. This combination of increased biological
activity and purity is what sets Receptor Grade IGF-1 LR3 apart
from standard IGF-1. Media grade LR3 IGF-I is more commonly used in
commercial cell culture vs mammalian. It can also be used as a
research reagent at an economical cost to enable studies where
biological potency is of less value and higher quantities are
required. To maximize results in an animal-based cell study or
production Receptor Grade IGF-1 Long R3 should be used exclusively.
IGFB Binding and Increased Biological Activity
By resisting IGFBP-binding, IGF-1 LR3 has a greater physiologic
effect than IGF-1 does. The longer duration of action allows for
smaller amounts to be used with the same effects. Some IGF-1
derivatives, such as the GPE derivative, made up of just the last
three N-terminal amino acids of the IGF-1 protein, have been shown
to have therapeutic effects in neurological injuries like stroke.
Most studies concerning the effects of IGF-1 derivatives have been
carried out in animal models, with little to no data available for
Insulin Like Growth Factor Receptor Interactions
IGF-1 Long R3 binds to at least two cell surface receptors: IGF-1R
and the insulin receptor. The IGF-1 receptor is referred to as the
"physiologic" receptor because IGF-1 binds to it with significantly
higher affinity (approximately 100 times higher) than it does to
the insulin receptor. By binding to IGF-1R, IGF-1 can affect
metabolism, cell growth (hypertrophy), differentiation and cell
division (hyperplasia), prevention of cell death (apoptosis),
normal development, and even malignant growth.
IGF-1R has been implicated in several different types of cancer
include breast, prostate, and lung cancer. IGF-1 also binds to the
insulin receptor and activates it, thereby encouraging cells to
take up glucose from the blood stream. The effects of IGF-1 on
muscle cells are three-fold. Firstly, IGF-1 encourages hyperplasia,
or an increase in the number of muscle cells. Secondly, IGF-1 has a
strong effect on skeletal muscle - In regards to the life span of
satellite cells. Satellite cells support muscle cells, providing
them with needed nutrients and helping them to operate efficiently.
By increasing the lifespan of these cells, IGF-1 helps to increase
their number with muscle tissue.
Finally, IGF-1 encourages differentiation of myoblasts, which is to
say that it encourages the conversion of stem cell progeny from
nonspecific pluripotent stem cells into dedicated muscle tissue. In
this way, IGF-1 increases the rate of muscle development by
increasing the rate at which generic stem cells are converted to