Whole Cells - Molecular Theory of the Living Cell - page 423

Table 12.9 Possible mechanisms of structural genes self-regulating the intracellular levels of
their own transcripts. An arrow can be read as “regulates.” The structural genes correspond to
“visible genes” in Fig. 12.22 , i.e., those genes whose transcripts are being measured, and those
genes whose transcripts are not measured directly but are assumed to affect the “visible genes”
in one way or another are referred to as “invisible genes” in Fig. 12.22
Mechanisms Details

1 A Structural genes ! RNA ! Transcription

2 B Structural genes

Other structural genes ! RNA ! Transcription

Structural genes ! RNA ! Transcript degradation 3 C

4 D Structural genes

Other structural genes ! RNA ! Transcription degradation

5 E Structural genes ! RNA ! Protein ! Transcription

6 F Structural genes

Other structural genes ! RNA ! Protein ! Transcript ion

7 G Structural genes ! RNA ! Protein ! Transcript degradation

8 H Structural genes

Other structural genes ! RNA ! Protein ! Transcript degradation

9 I c 1 A+c 2 B+c 3 C+c 4 D+c 5 E+c 6 F+c 7 G+c 8 H

where c 1 -c 8 are positive fractions adding up to 1

protein machines as exemplified by supercoiled DNA. This leads me to suggest that
molecular machines be divided into three groups as shown in Fig. 12.23 , in analogy
to the division of transport processes into a similar scheme.
Utilizing the machine classification scheme shown in Fig. 12.23 , the following
generalization may be proposed:
d-Genes cannot act as primary active molecular machines but can act only as secondary
active molecular machines (SAMM) or passive molecular machines (PMM). (12.25)

Statement 12.25 may be referred to as the “d-Gene as Molecular Machines
(DGAMM)” hypothesis. Since structural genes are members of the drp-gene family
(Sect. 11.2.4 ) , the hypothesis that structural genes are molecular machines would
follow as a corollary from the DGAMM hypothesis.