There are three type of Splicing signals 

 Major U2-type or GU-AG introns

Minor U12-type or AU-AC introns

Minor U12-type with GU-AG introns (hybrid type)

TLS Online TPP Program

#Id: 7913

#Unit 2. Cellular Organization

Matrix-targeting sequences

sequences for localizing proteins to mitochondria

TLS Online TPP Program

#Id: 7914

#Unit 2. Cellular Organization

Matrix-targeting sequences

Located at the N-terminus

Usually 20–50 amino acids in length

Rich in hydrophobic amino acids, positively charged basic amino acids (arginine & lysine), and hydroxylated ones (serine and threonine)

Amphipathicity of matrix-targeting sequences is critical to their function

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#Id: 7915

#Unit 2. Cellular Organization

Mitochondrial protein import requires: 

Tom proteins (Tom 20/22/70)

General import pore (Tom40)

Tim proteins (Tim23/17)

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#Id: 7916

#Unit 2. Cellular Organization

Energy inputs are needed to Import proteins into mitochondria

Chaperone proteins (Hsp70& Hsp90)

An H+ electrochemical gradient, or proton-motive force

TLS Online TPP Program

#Id: 7917

#Unit 2. Cellular Organization

Brown Adipose Tissue

is brown because of the presence of large numbers of mitochondria (high concentrations of cytochromes), with heme groups that are strong absorbers of visible 

TLS Online TPP Program

#Id: 7918

#Unit 2. Cellular Organization